National Grid (NGG) 6-K7 Nov 24Current report (foreign)Financial data

Company Profile

Cover Page

Cover Page	6 Months Ended
Cover Page	Sep. 30, 2024
Cover [Abstract]
Document Type	6-K
Entity Registrant Name	NATIONAL GRID PLC
Amendment Flag	false
Entity Central Index Key	0001004315
Current Fiscal Year End Date	--03-31
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q2

Consolidated income statement

Consolidated income statement - GBP (£) £ in Millions	6 Months Ended
Consolidated income statement - GBP (£) £ in Millions	Sep. 30, 2024	Sep. 30, 2023
Profit or loss [abstract]
Revenue	£ 7,961	£ 8,489
Provision for bad and doubtful debts	(81)	(91)
Other operating costs	(6,571)	(6,425)
Other operating income		12
Operating profit	1,309	1,985
Finance income	234	115
Finance costs	(916)	(800)
Share of post-tax results of joint ventures and associates	57	71
Profit before tax	684	1,371
Tax	(112)	(307)
Profit after tax from continuing operations	572	1,064
Profit after tax from discontinued operations	76	65
Total profit for the period (continuing and discontinued)	648	1,129
Attributable to:
Equity shareholders of the parent	647	1,128
Non-controlling interests	£ 1	£ 1
Earnings per share (pence)
Basic earnings per share (continuing) (in GBP per share)	£ 0.126	£ 0.267	[1]
Diluted earnings per share (continuing) (in GBP per share)	0.126	0.266	[1]
Basic earnings per share (continuing and discontinued) (in GBP per share)	0.143	0.283	[1]
Diluted earnings per share (continuing and discontinued) (in GBP per share)	£ 0.142	£ 0.282	[1]

[1] Restated to reflect the impact of the bonus element of the Rights Issue (see note 9).

Consolidated statement of compr

Consolidated statement of comprehensive income - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Statement of comprehensive income [abstract]
Profit after tax from continuing operations	£ 572	£ 1,064
Profit after tax from discontinued operations	76	65
Items from continuing operations that will never be reclassified to profit or loss:
Remeasurement gains/(losses) on pension assets and post-retirement benefit obligations	51	(263)
Net losses in respect of cash flow hedging of capital expenditure	(25)	(2)
Tax on items that will never be reclassified to profit or loss	(8)	64
Total items from continuing operations that will never be reclassified to profit or loss	18	(201)
Items from continuing operations that may be reclassified subsequently to profit or loss:
Retranslation of net assets offset by net investment hedge	(799)	118
Net gains in respect of cash flow hedges	78	201
Net (losses)/gains in respect of cost of hedging	(12)	40
Net gains/(losses) on investments in debt instruments measured at fair value through other comprehensive income	13	(16)
Tax on items that may be reclassified subsequently to profit or loss	(17)	(59)
Total items from continuing operations that may be reclassified subsequently to profit or loss	(737)	284
Other comprehensive (loss)/income for the period, net of tax, from continuing operations	(719)	83
Other comprehensive loss for the period, net of tax, from discontinued operations	(10)	(9)
Other comprehensive (loss)/income for the period, net of tax	(729)	74
Total comprehensive (loss)/income for the period from continuing operations	(147)	1,147
Total comprehensive income for the period from discontinued operations	66	56
Total comprehensive (loss)/income for the period	(81)	1,203
Attributable to:
Equity shareholders of the parent from continuing operations	(147)	1,146
Equity shareholders of the parent from discontinued operations	66	56
Equity shareholders of the parent	(81)	1,202
Non-controlling interests	£ 0	£ 1

Consolidated statement of chang

Consolidated statement of changes in equity - GBP (£) £ in Millions	Total	Total share-holders’ equity	Share capital	Share premium account	Retained earnings	Other equity reserves	Non-controlling interests
Equity, beginning balance at Mar. 31, 2023	£ 29,562	£ 29,538	£ 488	£ 1,302	£ 31,608	£ (3,860)	£ 24
Profit for the period	1,129	1,128			1,128		1
Other comprehensive income/(loss) for the period	74	74			(199)	273
Total comprehensive (loss)/income for the period	1,203	1,202			929	273	1
Equity dividends	(1,325)	(1,325)			(1,325)
Scrip dividend-related share issue	0	0	1	(1)
Issue of treasury shares	20	20			20
Transactions in own shares	(1)	(1)			(1)
Share-based payments	19	19			19
Cash flow hedges transferred to the statement of financial position, net of tax	2	2				2
Equity, ending balance at Sep. 30, 2023	29,480	29,455	489	1,301	31,250	(3,585)	25
Equity, beginning balance at Mar. 31, 2024	29,892	29,867	493	1,298	32,066	(3,990)	25
Profit for the period	648	647			647		1
Other comprehensive income/(loss) for the period	(729)	(728)			38	(766)	(1)
Total comprehensive (loss)/income for the period	(81)	(81)			685	(766)	0
Rights Issue	6,839	6,839	135			6,704
Transfer between reserves	0	0			6,704	(6,704)
Equity dividends	(811)	(811)			(811)
Scrip dividend-related share issue	0	0	9	(9)
Issue of treasury shares	15	15			15
Transactions in own shares	(5)	(5)			(5)
Share-based payments	16	16			16
Cash flow hedges transferred to the statement of financial position, net of tax	1	1				1
Equity, ending balance at Sep. 30, 2024	£ 35,866	£ 35,841	£ 637	£ 1,289	£ 38,670	£ (4,755)	£ 25

Consolidated statement of finan

Consolidated statement of financial position - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Non-current assets
Goodwill	£ 9,367	£ 9,729
Other intangible assets	3,393	3,431
Property, plant and equipment	69,195	68,907
Other non-current assets	850	848
Pension assets	2,478	2,407
Financial and other investments	795	880
Investments in joint ventures and associates	901	1,420
Derivative financial assets	413	324
Total non-current assets	87,392	87,946
Current assets
Inventories and current intangible assets	639	828
Trade and other receivables	2,661	3,415
Current tax assets	19	11
Financial and other investments	6,140	3,699
Derivative financial assets	145	44
Cash and cash equivalents	1,125	559
Assets held for sale	3,731	1,823
Total current assets	14,460	10,379
Total assets	101,852	98,325
Current liabilities
Borrowings	(2,703)	(4,859)
Derivative financial liabilities	(419)	(335)
Trade and other payables	(3,969)	(4,076)
Contract liabilities	(91)	(127)
Current tax liabilities	(181)	(220)
Provisions	(314)	(298)
Liabilities held for sale	(1,309)	(1,474)
Total current liabilities	(8,986)	(11,389)
Non-current liabilities
Borrowings	(42,473)	(42,213)
Derivative financial liabilities	(854)	(909)
Other non-current liabilities	(848)	(880)
Contract liabilities	(2,200)	(2,119)
Deferred tax liabilities	(7,357)	(7,519)
Pensions and other post-retirement benefit obligations	(603)	(593)
Provisions	(2,665)	(2,811)
Total non-current liabilities	(57,000)	(57,044)
Total liabilities	(65,986)	(68,433)
Net assets	35,866	29,892
Equity
Share capital	637	493
Share premium account	1,289	1,298
Retained earnings	38,670	32,066
Other equity reserves	(4,755)	(3,990)
Total shareholders’ equity	35,841	29,867
Non-controlling interests	25	25
Total equity	£ 35,866	£ 29,892

Consolidated cash flow statemen

Consolidated cash flow statement - GBP (£) £ in Millions	6 Months Ended
Consolidated cash flow statement - GBP (£) £ in Millions	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities
Operating profit from continuing operations	£ 1,309	£ 1,985
Adjustments for:
Other fair value movements	21	(19)
Depreciation, amortisation and impairment	1,058	1,021
Share-based payments	16	19
Changes in working capital	442	(10)
Changes in provisions	(180)	39
Changes in pensions and other post-retirement benefit obligations	24	27
Cash generated from operations – continuing operations	2,690	3,062
Tax paid	(78)	(201)
Net cash flow from operating activities – continuing operations	2,612	2,861
Net cash flow from operating activities – discontinued operations	0	0
Cash flows from investing activities
Purchases of intangible assets	(243)	(269)
Purchases of property, plant and equipment	(3,985)	(3,210)
Disposals of property, plant and equipment	10	18
Investments in joint ventures and associates	(102)	(151)
Dividends received from joint ventures, associates and other investments	71	121
Disposal of financial and other investments	33	65
Acquisition of financial investments	(49)	(32)
Net movements in short-term financial investments	(2,995)	885
Interest received	162	69
Cash inflows on derivatives	0	103
Cash outflows on derivatives	(6)	(4)
Net cash flow used in investing activities – continuing operations	(6,418)	(2,410)
Net cash flow from investing activities – discontinued operations	22	0
Cash flows from financing activities
Proceeds of Rights Issue	7,001	0
Transaction fees related to Rights Issue	(162)	0
Proceeds from issue of treasury shares	15	20
Transactions in own shares	(5)	(1)
Proceeds received from loans	1,809	3,033
Repayments of loans	(916)	(839)
Payments of lease liabilities	(75)	(61)
Net movements in short-term borrowings	(1,313)	(444)
Cash inflows on derivatives	73	68
Cash outflows on derivatives	(33)	(60)
Interest paid	(1,002)	(779)
Dividends paid to shareholders	(811)	(1,325)
Net cash flow from/(used in) financing activities – continuing operations	4,581	(388)
Net cash flow from financing activities – discontinued operations	0	0
Net increase in cash and cash equivalents	797	63
Reclassification to held for sale	(166)	0
Exchange movements	(65)	1
Net cash and cash equivalents at start of period	559	163
Net cash and cash equivalents at end of period	1,125	227
UK Gas Transmission
Cash flows from investing activities
Disposal of interest in the UK Gas Transmission business	686	0
National Grid Renewables and Emerald Energy Venture LLC
Cash flows from investing activities
Contributions to National Grid Renewables and Emerald Energy Venture LLC	£ 0	£ (5)

Basis of preparation and new ac

Basis of preparation and new accounting standards, interpretations and amendments	6 Months Ended
	Sep. 30, 2024
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Basis of preparation and new accounting standards, interpretations and amendments	1. Basis of preparation and new accounting standards, interpretations and amendments The half year financial information covers the six month periods ended 30 September 2024 and 30 September 2023 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB). This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2024 and 2023, together with the audited consolidated statement of financial position as at 31 March 2024. The half year financial information has been prepared applying consistent accounting policies to those applied by the Group for the year ended 31 March 2024. The notes to the unaudited financial information are prepared on a continuing basis unless otherwise stated. The financial information for the six months ended 30 September 2024 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2024, which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB. The key sources of estimation uncertainty and areas of judgement for the period ended 30 September 2024 are aligned to those disclosed in the Annual Report and Accounts for year ended 31 March 2024, with the following amendments: • in relation to the planned disposals of Grain LNG, our UK LNG business, and National Grid Renewables Development LLC (NG Renewables), our US onshore renewables business, judgement has been applied in concluding that the criteria required for held for sale classification have been met (see note 6); and • the classification of our 20% equity investment in GasT TopCo Limited, together with the Remaining Acquisition Agreement (RAA) over the remaining interest, as held for sale is no longer considered to represent an area of judgement following the disposal on 26 September 2024 (see note 6). 1. Basis of preparation and new accounting standards, interpretations and amendments continued Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 56) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale (see note 6); • adverse impacts of higher spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2024, the Group had undrawn committed facilities available for general corporate purposes amounting to £7.7 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£1.8 billion of new long-term senior debt issued in the period from 1 April to 30 September 2024 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information. New IFRS accounting standards, interpretations and amendments adopted in the period
Basis of preparation and new accounting standards, interpretations and amendments	1. Basis of preparation and new accounting standards, interpretations and amendments The half year financial information covers the six month periods ended 30 September 2024 and 30 September 2023 and has been prepared in accordance with IAS 34 ‘Interim Financial Reporting’ as issued by the International Accounting Standards Board (IASB). This condensed set of financial statements comprises the unaudited financial information for the half years ended 30 September 2024 and 2023, together with the audited consolidated statement of financial position as at 31 March 2024. The half year financial information has been prepared applying consistent accounting policies to those applied by the Group for the year ended 31 March 2024. The notes to the unaudited financial information are prepared on a continuing basis unless otherwise stated. The financial information for the six months ended 30 September 2024 does not constitute statutory accounts as defined in Section 434 of the Companies Act 2006. It should be read in conjunction with the statutory accounts for the year ended 31 March 2024, which were prepared in accordance with International Financial Reporting Standards (IFRS) as issued by the IASB. The key sources of estimation uncertainty and areas of judgement for the period ended 30 September 2024 are aligned to those disclosed in the Annual Report and Accounts for year ended 31 March 2024, with the following amendments: • in relation to the planned disposals of Grain LNG, our UK LNG business, and National Grid Renewables Development LLC (NG Renewables), our US onshore renewables business, judgement has been applied in concluding that the criteria required for held for sale classification have been met (see note 6); and • the classification of our 20% equity investment in GasT TopCo Limited, together with the Remaining Acquisition Agreement (RAA) over the remaining interest, as held for sale is no longer considered to represent an area of judgement following the disposal on 26 September 2024 (see note 6). 1. Basis of preparation and new accounting standards, interpretations and amendments continued Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 56) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale (see note 6); • adverse impacts of higher spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2024, the Group had undrawn committed facilities available for general corporate purposes amounting to £7.7 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£1.8 billion of new long-term senior debt issued in the period from 1 April to 30 September 2024 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information. New IFRS accounting standards, interpretations and amendments adopted in the period

Segmental analysis

Segmental analysis	6 Months Ended
Segmental analysis	Sep. 30, 2024
Disclosure of operating segments [abstract]
Segmental analysis	2. Segmental analysis Revenue and the results of the business are analysed by operating segment, based on the information the Board use internally for the purposes of evaluating the performance of each operating segment and determining resource allocation between them. The Board is National Grid’s chief operating decision maker (as defined by IFRS 8 ‘Operating Segments’) and assesses the profitability of a profit measure that excludes certain income and expenses. We call that measure ‘adjusted profit’. Adjusted profit excludes exceptional items and remeasurements (as defined in note 4) and is used by management to monitor financial performance as it is considered that it aids the comparability of our reported financial performance from year to year. As a matter of course, the Board also considers profitability by segment, excluding the effect of major storms, timing adjustments relating to revenue, certain pass-through costs and deferred tax for our UK Electricity Transmission and UK Electricity Distribution businesses. However, the measure of profit disclosed in this note is operating profit before exceptional items and remeasurements, as this is the measure that is most consistent with the IFRS results reported within these financial statements. The results of our six principal businesses are reported to the Board and are accordingly treated as reportable operating segments. All other operating segments are either reported to the Board on an aggregated basis or do not meet the quantitative threshold in order to be considered a separate operating segment. The following table describes the main activities for each reportable operating segment: UK Electricity Transmission The high-voltage electricity transmission networks in England and Wales. This includes our Accelerated Strategic Transmission Investment projects to connect more clean, low-carbon power to the transmission network in England and Wales. UK Electricity Distribution The electricity distribution networks of NGED in the East Midlands, West Midlands and South West of England and South Wales. UK Electricity System Operator The Great Britain system operator which is classified as held for sale (see note 6). New England Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New England. New York Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New York. National Grid Ventures Comprises all commercial operations in LNG at the Isle of Grain in the UK (Grain LNG) and Providence, Rhode Island in the US, our electricity generation business in the US, our electricity interconnectors in the UK and our investment in NG Renewables, our renewables business in the US. Whilst NGV operates outside our regulated core business, the electricity interconnectors in the UK are subject to indirect regulation by Ofgem regarding the level of returns they can earn. NG Renewables and Grain LNG were classified as held for sale at 30 September 2024 (see note 6). The New England and New York segments typically experience seasonal fluctuations in revenue and operating profit due to higher delivery volumes during the second half of the financial year, for example as a result of colder weather over the winter months driving increased heating demand. These seasonal fluctuations have a consequential impact on the working capital balances (primarily trade debtors and accrued income) in the consolidated statement of financial position at 30 September 2024 when compared to 31 March 2024. The majority of UK revenues are derived from the supply of network capacity rather than the supply of commodities and therefore are not subject to the same seasonal fluctuations as in New York and New England. Other activities that do not form part of any of the segments in the above table primarily relate to our UK property business together with insurance and corporate activities in the UK and US and the Group’s investments in technology and innovation companies through National Grid Partners. 2. Segmental analysis continued (a) Revenue Six months ended 30 September 2024 2023 Total sales Sales between segments 1 Sales to third parties Total sales Sales between segments 1 Sales to third £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 1,274 (92) 1,182 1,356 (19) 1,337 UK Electricity Distribution 1,166 (2) 1,164 850 (2) 848 UK Electricity System Operator 1,029 (17) 1,012 1,734 (17) 1,717 New England 1,545 — 1,545 1,441 — 1,441 New York 2,341 — 2,341 2,365 — 2,365 National Grid Ventures 650 (26) 624 666 (27) 639 Other 98 (5) 93 142 — 142 Total revenue from continuing operations 8,103 (142) 7,961 8,554 (65) 8,489 Geographical areas: UK 3,755 4,309 US 4,206 4,180 Total revenue from continuing operations 7,961 8,489 1. Sales between operating segments are priced having regard to the regulatory and legal requirements to which the businesses are subject. The analysis of revenue by geographical area is on the basis of destination. There are no material sales between the UK and US geographical areas. (b) Operating profit/(loss) Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 642 839 — (1) 642 838 UK Electricity Distribution 764 476 (5) (4) 759 472 UK Electricity System Operator (364) 443 151 — (213) 443 New England 89 (32) (2) (15) 87 (47) New York (30) (30) (20) 38 (50) 8 National Grid Ventures 147 219 (2) 91 145 310 Other (38) (13) (23) (26) (61) (39) Total operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Geographical areas: UK 1,173 1,956 121 60 1,294 2,016 US 37 (54) (22) 23 15 (31) Total operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m Reconciliation to profit before tax: Operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Share of post-tax results of joint ventures and associates 60 59 (3) 12 57 71 Finance income 231 123 3 (8) 234 115 Finance costs (901) (834) (15) 34 (916) (800) Total profit before tax from continuing operations 600 1,250 84 121 684 1,371 2. Segmental analysis continued The following items are included in the total operating profit by segment: Depreciation, amortisation and impairment 30 September 2024 30 September 2023 £m £m Operating segments: UK Electricity Transmission (267) (250) UK Electricity Distribution (122) (105) UK Electricity System Operator — (52) New England (221) (204) New York (351) (321) National Grid Ventures (92) (84) Other (5) (5) Total (1,058) (1,021) Asset type: Property, plant and equipment (936) (868) Non-current intangible assets (122) (153) Total (1,058) (1,021) (c) Capital investment Capital investment represents additions to property, plant and equipment, prepayments to suppliers to secure production capacity in relation to our capital projects, non-current intangibles and additional equity investments in joint ventures and associates. Segmental information used for internal decision making was revised in the year ended 31 March 2024 to include capital expenditure prepayments and additional equity investments in joint ventures and associates. Capital investments exclude additions for assets or businesses from the point they are classified as held for sale. 30 September 2024 30 September 2023¹ £m £m Operating segments: UK Electricity Transmission 1,290 899 UK Electricity Distribution 647 608 UK Electricity System Operator — 75 New England 814 789 New York 1,569 1,257 National Grid Ventures 279 316 Other 4 2 Total 4,603 3,946 Asset type: Property, plant and equipment 4,200 3,413 Non-current intangible assets 196 257 Equity investments in joint ventures and associates 102 151 Capital expenditure prepayments 105 125 Total 4,603 3,946 1. Comparative amounts have been represented to reflect the change in presentation for capital investments. (d) Geographical analysis of non-current assets Non-current assets by geography comprise goodwill, other intangible assets, property, plant and equipment, investments in joint ventures and associates and other non-current assets. 30 September 2024 31 March 2024 £m £m Split by geographical area: UK 40,738 40,065 US 42,968 44,270 Total 83,706 84,335 Reconciliation to total non-current assets: Pension assets 2,478 2,407 Financial and other investments 795 880 Derivative financial assets 413 324 Non-current assets 87,392 87,946

Revenue

Revenue	6 Months Ended
Revenue	Sep. 30, 2024
Revenue [abstract]
Revenue	3. Revenue Under IFRS 15 ‘Revenue from Contracts with Customers’, revenue is recorded as or when the Group satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is transferred when the customer obtains control of that good or service. The transfer of control of our distribution or transmission services coincides with the use of our network, as electricity and gas pass through our network and reach our customers. The Group principally satisfies its performance obligations over time and the amount of revenue recorded corresponds to the amounts billed and accrued for volumes of gas and electricity delivered/transferred to/from our customers. Revenue for the six months ended 30 September 2024 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New New National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,116 — 46 46 126 430 — 1,764 Distribution — 1,113 — 1,468 2,181 — 1 4,763 System Operator — — 966 — — — — 966 Other 1 16 49 — 4 8 43 — 120 Total IFRS 15 revenue 1,132 1,162 1,012 1,518 2,315 473 1 7,613 Other revenue Generation — — — — — 191 — 191 Other 2 50 2 — 27 26 (40) 92 157 Total other revenue 50 2 — 27 26 151 92 348 Total revenue from continuing operations 1,182 1,164 1,012 1,545 2,341 624 93 7,961 Geographic split of revenue for the six months ended 30 September 2024 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New National Grid Ventures Other Total Revenue under IFRS 15 UK 1,132 1,162 1,012 — — 430 — 3,736 US — — — 1,518 2,315 43 1 3,877 Total IFRS 15 revenue 1,132 1,162 1,012 1,518 2,315 473 1 7,613 Other revenue UK 50 2 — — — (38) 5 19 US — — — 27 26 189 87 329 Total other revenue 50 2 — 27 26 151 92 348 Total revenue from continuing operations 1,182 1,164 1,012 1,545 2,341 624 93 7,961 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated by NG Renewables which was classified as held for sale in the period (see note 6). 2. Other revenue, recognised in accordance with accounting standards other than IFRS 15, includes property sales by our UK commercial property business, net fair value gains and losses in respect of investments in our National Grid Partners business, rental income, income arising in connection with the Transition Services Agreements in place following the sales of NECO and the UK Gas Transmission businesses and the planned sale of the ESO, and an adjustment to NGV revenue in respect of the interconnector cap and floor and Use of Revenue regimes constructed by Ofgem. 3. Revenue continued Revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,299 — 5 43 283 426 — 2,056 Distribution — 810 — 1,329 2,047 — — 4,186 System Operator — — 1,712 — — — — 1,712 Other 1 9 36 — 4 7 75 — 131 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue Generation — — — — — 181 — 181 Other 2 29 2 — 65 28 (43) 142 223 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 Geographic split of revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures Other Total Revenue under IFRS 15 UK 1,308 846 1,717 — — 430 — 4,301 US — — — 1,376 2,337 71 — 3,784 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue UK 29 2 — — — (50) 27 8 US — — — 65 28 188 115 396 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated by NG Renewables. 2.

Exceptional items and remeasure

Exceptional items and remeasurements	6 Months Ended
Exceptional items and remeasurements	Sep. 30, 2024
Exceptional Items And Remeasurements [Abstract]
Exceptional items and remeasurements	4. Exceptional items and remeasurements To monitor our segmental financial performance, we use an adjusted consolidated profit measure that excludes certain income and expenses. We exclude items from adjusted profit because, if included, these items could distort understanding of our performance in the period and the comparability between periods. With respect to restructuring and transformation costs, these represent additional expenses incurred that are not related to normal business and day‑to-day activities. These can take place over multiple reporting periods given the scale of the Group, the nature and complexity of the transformation initiatives and due to the impact of strategic transactions. In assessing items to exclude from adjusted profit, management uses an exceptional items framework that has been discussed and approved by the Audit & Risk Committee, as detailed in note 5 of the Annual Report and Accounts for the year ended 31 March 2024. Remeasurements comprise unrealised gains or losses recorded in the consolidated income statement arising from changes in the fair value of certain financial assets and liabilities categorised as held at fair value through profit and loss (FVTPL). Once the fair value movements are realised (for example, when the derivative matures), the previously recognised fair value movements are then reversed through remeasurements and recognised within earnings before exceptional items and remeasurements. These assets and liabilities include commodity contracts and derivative financial instruments to the extent that hedge accounting is either not achieved or is not effective. We have also classified the unrealised gains or losses reported in profit and loss on certain additional assets treated as FVTPL within remeasurements. These relate to financial assets (which fail the ‘solely payments of principal and interest test’ under IFRS 9), the money market fund investments used by Group Treasury for cash management purposes and the net foreign exchange gains and losses on borrowing activities. These are offset by foreign exchange gains and losses on financing derivatives measured at fair value. In all cases, these fair values increase or decrease because of changes in foreign exchange, commodity or other financial indices over which we have no control. Six months ended 30 September 2024 Exceptional items Remeasurements Total Included within operating profit from continuing operations Provision for UK electricity balancing costs 151 — 151 Major transformation programme (42) — (42) Changes in environmental provisions (1) — (1) Net losses on commodity contract derivatives — (9) (9) 108 (9) 99 Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations Cost efficiency programme (39) — (39) Transaction, separation and integration costs 1 (11) — (11) IFA1 fire insurance proceeds 92 — 92 Net gains on commodity contract derivatives — 41 41 42 41 83 1. Transaction, separation and integration costs represent the aggregate of distinct activities undertaken by the Group. Provision for UK electricity balancing costs: During the year ended 31 March 2024, the ESO’s operating profit increased due to a substantial over-recovery of allowed revenues received under its regulatory framework. Under IFRS a corresponding liability is not recognised for the return of over-recoveries as this relates to future customers and services that have not yet been delivered. Following legislation to enable the separation of the ESO and the formation of the National Energy System Operator (NESO), the Group recognised a liability of £498 million representing the element of the over-recovery that would be settled through the sale process, as detailed in note 5 of the Annual Report and Accounts for the year ended 31 March 2024. In the period, the liability has been remeasured to reflect the final amount of over-recovered revenues which will transfer through the disposal which completed on 1 October 2024 (see note 6). 4. Exceptional items and remeasurements continued Major transformation programme: Following the announcement of our new strategic priorities in May 2024, the Group entered into a new four Changes in environmental provisions: In the US, we recognise environmental provisions related to the remediation of the Gowanus Canal, Newtown Creek and the former manufacturing gas plant facilities previously owned or operated by the Group or its predecessor companies. The sites are subject to both state and federal environmental remediation laws in the US. Potential liability for the historical contamination may be imposed on responsible parties jointly and severally, without regard to fault, even if the activities were lawful when they occurred. The provisions and the Group’s share of estimated costs are re-evaluated at each reporting period. During the period, following discussions with the New York State Department of Environmental Conservation and the Environmental Protection Agency on the scope and design of remediation activities related to certain of our responsible sites, we have re-evaluated our estimates of total costs and recognised net movements of £1 million in relation to our provisions. Under the terms of our rate plans, we are entitled to recovery of environmental clean-up costs from rate payers in future reporting periods. Such recoveries through overall allowed revenues are not classified as exceptional in the future periods that they occur due to the extended duration over which such costs are recovered and the immateriality of the recoveries in any given year. Cost efficiency programme: During the prior period, the Group incurred a further £39 million of costs in relation to the major cost efficiency programme announced in November 2021, that targeted at least £400 million savings per annum across the Group by the end of three years. The costs recognised primarily related to redundancy provisions, employee costs and professional fees incurred in delivering the programme. The total cash outflow in relation to these costs was £28 million. The cost efficiency programme completed in the year ended 31 March 2024, with total costs of £207 million recognised over the duration of the programme. Transaction, separation and integration costs: During the prior period, the Group incurred £11 million of transaction and separation costs in relation to the disposals of NECO and the UK Gas Transmission business (see note 6) and the integration of NGED. The costs incurred primarily related to legal fees, professional fees, and employee costs. The total cash outflow in relation to these costs for the period was £9 million. IFA1 interconnector insurance recovery: In September 2021, a fire at the IFA1 converter station in Sellindge, Kent caused significant damage to infrastructure on-site. In the prior period, the Group recognised net insurance claims of £92 million which were recognised as exceptional in line with our exceptional items policy and consistent with previous related claims. The total cash inflow for the period was £nil. 4. Exceptional items and remeasurements continued Details of remeasurements, tax exceptional items and the tax effect of exceptional items and remeasurements are also provided in this note. Six months ended 30 September 2024 Exceptional items Remeasurements Total Included within operating profit from continuing operations 108 (9) 99 Included within net finance costs (note 5) Net losses on derivative financial instruments — (15) (15) Net gains on financial assets at fair value through profit and loss — 3 3 — (12) (12) Included within share of post-tax results of joint ventures and associates Net losses on financial instruments — (3) (3) — (3) (3) Total included within profit before tax from continuing operations 108 (24) 84 Tax on exceptional items and remeasurements 11 6 17 Total exceptional items and remeasurements after tax from 119 (18) 101 Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations 42 41 83 Included within net finance costs (note 5) Net gains on derivative financial instruments — 34 34 Net losses on financial assets at fair value through profit and loss — (8) (8) — 26 26 Included within share of post-tax results of joint ventures and associates Net gains on financial instruments — 12 12 — 12 12 Total included within profit before tax from continuing operations 42 79 121 Tax on exceptional items and remeasurements 1 (21) (20) Total exceptional items and remeasurements after tax from 43 58 101

Finance income and costs

Finance income and costs	6 Months Ended
Finance income and costs	Sep. 30, 2024
Analysis of income and expense [abstract]
Finance income and costs	5. Finance income and costs 2024 2023 Six months ended 30 September £m £m Finance income Interest income from financing activities 143 52 Net interest on pensions and other post-retirement benefit obligations 50 51 Net gains/(losses) on financial assets at fair value through profit and loss 3 (8) Other interest income 38 20 234 115 Finance costs Interest expense on financial instruments 1 (950) (903) Unwinding of discount on provisions and other liabilities (64) (50) Other interest (21) (8) Net (losses)/gains on derivative financial instruments 2 (15) 34 Less: interest capitalised 3 134 127 (916) (800) Net finance costs from continuing operations (682) (685) 1. Finance costs include principal accretion on inflation-linked debt of £87 million (2023: £149 million) and income related to principal accretion on inflation-linked swaps of £4 million (2023: £18 million expense). 2. Includes a net foreign exchange gain on borrowing activities, offset by foreign exchange gains and losses on financing derivatives measured at fair value. 3. Interest on funding attributable to assets in the course of construction in the current period was capitalised at a rate of 4.3% (2023: 4.7%). In the UK, capitalised interest qualifies for a current year tax deduction with tax relief claimed of £16 million (2023: £21 million). In the US, capitalised interest is added to the cost of property, plant and equipment and qualifies for tax depreciation allowances.

Assets held for sale and discon

Assets held for sale and discontinued operations	6 Months Ended
Assets held for sale and discontinued operations	Sep. 30, 2024
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Assets held for sale and discontinued operations	6. Assets held for sale and discontinued operations Assets and businesses are classified as held for sale when their carrying amounts are recovered through sale rather than through continuing use. They only meet the held for sale condition when the assets are ready for immediate sale in their present condition, management is committed to the sale and it is highly probable that the sale will complete within one year. Once assets and businesses are classified as held for sale, depreciation and equity accounting ceases and the assets and businesses are remeasured if their carrying value exceeds their fair value less expected costs to sell. The results and cash flows of assets or businesses classified as held for sale or sold during the year, that meet the criteria of being a major separate line of business or geographical area of operation, are shown separately from our continuing operations, and presented within discontinued operations in the income statement and cash flow statement. The following assets and liabilities were classified as held for sale: 30 September 2024 31 March 2024 Total assets Total liabilities held for sale Net assets/(liabilities) held for sale £m Total assets Total liabilities held for sale Net assets/(liabilities) held for sale £m UK Electricity System Operator 1,549 (992) 557 1,134 (1,427) (293) National Grid Renewables 1,146 (10) 1,136 — — — Grain LNG 1,036 (307) 729 — — — Investment in GasT TopCo Limited — — — 689 — 689 RAA — — — — (47) (47) Net assets/(liabilities) held for sale 3,731 (1,309) 2,422 1,823 (1,474) 349 UK Electricity System Operator In October 2023, legislation required to enable the separation of the ESO and the formation of the NESO, which will undertake responsibilities across both the electricity and gas systems, was passed through Parliament. The assets and liabilities of the ESO were consequently presented as held for sale in the consolidated financial statements in the year ended 31 March 2024. The disposal subsequently completed on 1 October 2024 for consideration of £630 million, subject to certain completion adjustments. The gain on disposal will be reported in the Annual Report and Accounts for the year ended 31 March 2025. Based on the scale and pass-through nature of the ESO, it is not considered a separate major line of business or geographic operation under IFRS 5 for treatment as a discontinued operation, and its disposal is not part of a single coordinated plan being undertaken by the Group. Accordingly, the results of the ESO have not been separately disclosed on the face of the income statement. The following assets and liabilities of the ESO were classified as held for sale at 30 September 2024. £m Intangible assets 485 Property, plant and equipment 121 Trade and other receivables 375 Pension asset 16 Cash and cash equivalents 51 Financial investments 501 Total assets 1,549 Borrowings (13) Other liabilities (632) Provision for UK electricity balancing costs (347) Total liabilities (992) Net assets 557 The ESO generated profit after tax of £103 million for the period ended 30 September 2024 (2023: £455 million profit). 6. Assets held for sale and discontinued operations continued NG Renewables and Grain LNG The Group has previously announced its intention to sell NG Renewables, its US onshore renewables business, and Grain LNG, its UK LNG asset. As both sales are considered to be highly probable and expected to complete within a year, the associated assets and liabilities have been presented as held for sale in the consolidated statement of financial position at 30 September 2024. However, as NG Renewables and Grain LNG do not represent separate major lines of business or geographical operations, they have not met the criteria for classification as discontinued operations and therefore their results for the period are not separately disclosed on the face of the income statement. The following assets and liabilities were classified as held for sale at 30 September 2024. National Grid Renewables Grain LNG £m £m Goodwill 80 — Other intangible assets — 5 Property, plant and equipment 90 856 Investments in joint ventures and associates 704 — Trade and other receivables 74 47 Cash and cash equivalents 39 106 Financial investments 23 — Other assets 136 22 Total assets 1,146 1,036 Borrowings (2) (120) Other liabilities (8) (187) Total liabilities (10) (307) Net assets 1,136 729 Upon disposal of NG Renewables, the Group will also release deferred income related to profits on previous sales to the joint venture Emerald Energy Venture LLC which are deferred in accordance with IAS 28. No impairment losses were recognised on reclassification of the NG Renewables and Grain LNG assets and liabilities classified to held for sale. The aggregate profit after tax for NG Renewables and Grain LNG for the period ended 30 September 2024 was £52 million (2023: £83 million). The UK Gas Transmission business On 31 January 2023, the Group disposed of 100% of the UK Gas Transmission business for cash consideration of £4.0 billion and a 40% interest in a newly incorporated UK limited company, GasT TopCo Limited. The other 60% was purchased by Macquarie Infrastructure and Real Assets (MIRA) and British Columbia Investment Management Corporation (BCI) (together, the ‘Consortium’). The Group also entered into a Further Acquisition Agreement (the FAA option) with the Consortium over its remaining 40% interest. Both the investment in GasT TopCo Limited and the FAA option were immediately classified as held for sale and the Group has not applied equity accounting in relation to its investment in GasT TopCo Limited. The FAA was partially exercised by the Consortium on 11 March 2024 and the Group disposed of 20% of the 40% interest in GasT TopCo Limited, as detailed in note 10 of the Annual Report and Accounts for the year ended 31 March 2024. As part of the transaction, the Group also entered into a new agreement with the Consortium, the RAA, to replace the FAA option for the potential sale of all or part of the remaining 20% equity interest in GasT TopCo Limited (the Remaining Interest). On 26 July 2024, the Consortium exercised its option under the RAA and the disposal of the Group’s remaining interest in GasT TopCo Limited completed on 26 September 2024. The total sales proceeds were £686 million and the gain on disposal, after transaction costs, was £25 million. 6. Assets held for sale and discontinued operations continued The disposal of the Group’s Remaining Interest in GasT TopCo Limited is the final stage of the plan to dispose of the UK Transmission business first announced in 2021. As a result, the gain on disposal and any remeasurements pertaining to the financial derivatives noted above are shown separately from the continuing business for all periods presented on the face of the income statement as a discontinued operation. This is also reflected in the statement of comprehensive income, as well as earnings per share (EPS) being shown split between continuing and discontinued operations. The summary income statements for the periods ended 30 September 2024 and 2023 are as follows: 2024 2023 £m £m Operating profit — — Finance income 5 9 Finance costs 1 47 61 Profit before tax 52 70 Tax (1) (5) Profit after tax from discontinued operations 51 65 Gain on disposal 25 — Total profit after tax from discontinued operations 76 65 1. Finance costs include the remeasurement of the FAA option, the FAA forward and the RAA. The summary statements of comprehensive income are as follows: 2024 2023 £m £m Profit after tax from discontinued operations 76 65 Other comprehensive (loss)/income from discontinued operations Items from discontinued operations that may be reclassified subsequently to profit or loss: Net losses on investments in debt instruments measured at fair value through other (13) (12) Tax on items that may be reclassified subsequently to profit or loss 3 3 Total losses from discontinued operations that may be reclassified subsequently to profit or loss (10) (9) Other comprehensive loss for the period, net of tax, from discontinued operations (10) (9) Total comprehensive income for the period from discontinued operations 66 56

Tax from continuing operations

Tax from continuing operations	6 Months Ended
Tax from continuing operations	Sep. 30, 2024
Income taxes paid (refund) [abstract]
Tax from continuing operations	7. Tax from continuing operations The tax charge from continuing operations for the six month period ended 30 September 2024 is £112 million (2023: £307 million). It is based on management’s estimate of the weighted average effective tax rate by jurisdiction expected for the full year. The effective tax rate is 16.4% (2023: 22.4%), which includes the impact of our share of post-tax results of joint ventures and associates. The effective tax rate for the year ended 31 March 2024 was 27.3% including the impact of our share of post-tax results of joint ventures and associates. The legislation implementing the Organisation for Economic Co-operation and Development’s (OECD) proposals for a global minimum corporation tax rate (Pillar Two) was enacted into UK law on 11 July 2023. The legislation includes an income inclusion rule and a domestic minimum tax, which together are designed to ensure a minimum effective tax rate of 15% in each country in which the Group operates. Similar legislation is being enacted by other governments around the world. The legislation became effective for National Grid from 1 April 2024. The Group has applied the mandatory exception in the UK to recognising and disclosing information about the deferred tax assets and liabilities related to Pillar Two income taxes in accordance with the amendments to IAS 12 published by the IASB on 23 May 2023. The Group does not expect there to be a material impact on our current period or future tax charges.

Earnings per share

Earnings per share	6 Months Ended
Earnings per share	Sep. 30, 2024
Earnings per share [abstract]
Earnings per share	8. Earnings per share The earnings per share (EPS) calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests. (a) Basic earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2024 2024 2023 2023¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 571 12.6 1,063 26.7 Profit after tax from discontinued operations attributable to the parent 76 1.7 65 1.6 Total profit after tax attributable to the parent 647 14.3 1,128 28.3 2024 2023¹ millions millions Weighted average number of shares – basic 4,526 3,981 1. Comparative amounts have been restated to reflect the impact of the bonus element of the Rights Issue (see note 9). (b) Diluted earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2024 2024 2023 2023¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 571 12.6 1,063 26.6 Profit after tax from discontinued operations attributable to the parent 76 1.6 65 1.6 Total profit after tax attributable to the parent 647 14.2 1,128 28.2 2024 2023¹ millions millions Weighted average number of shares – diluted 4,547 3,999 1. Comparative amounts have been restated to reflect the impact of the bonus element of the Rights Issue (see note 9).

Rights Issue

Rights Issue	6 Months Ended
Rights Issue	Sep. 30, 2024
Issued capital [abstract]
Rights Issue	9. Rights Issue In June 2024, the Company completed a Rights Issue to support the future capital investment plans of the Group. The Company raised £6,839 million (net of expenses of £162 million) through the issue of 1,085 million new ordinary shares at 645 pence each on the basis of 7 new ordinary shares for every 24 existing ordinary shares. The issue price represented a discount of 33% to the closing ex-div share price on 23 May 2024, the announcement date of the Rights Issue. The structure of the Rights Issue gave rise to a merger reserve, representing the net proceeds of the Rights Issue less the nominal value of the new shares issued. Following the receipt of the cash proceeds through the structure, the excess of the net proceeds over the nominal value of the share capital issued was considered realised and has been transferred from the merger reserve to retained earnings. The discount element inherent in the Rights Issue is treated as a bonus issue of shares. Basic and diluted earnings per share figures have been restated for the comparative period, by adjusting the weighted average number of shares for a factor of 1.0811 to reflect the bonus element of the June 2024 Rights Issue, in accordance with IAS 33 Earnings per Share (note 8). For comparability, dividends per share are also restated after taking account of the bonus element of the Rights Issue, in note 10. Allotted, called up and fully paid shares of 12 204 ⁄ 473 pence each: Allotted, called-up and fully paid Shares Nominal value million £m At 1 April 2024 3,967 493 Issued in Rights Issue 1,085 135 Issued during the period in lieu of dividends 1 74 9 At 30 September 2024 2 5,126 637 1. The issue of shares under the scrip dividend programme is considered to be a bonus issue under the terms of the Companies Act 2006, and the nominal value of the shares is charged to the share premium account. 2. At 30 September 2024, the Company held 241 million (31 March 2024: 247 million) of its own shares.

Dividends

Dividends	6 Months Ended
Dividends	Sep. 30, 2024
Subclassifications of assets, liabilities and equities [abstract]
Dividends	10. Dividends Pence Cash Scrip Ordinary dividends Final dividend in respect of the year ended 31 March 2024 39.12 811 643 Interim dividend in respect of the year ended 31 March 2024 19.40 393 320 Final dividend in respect of the year ended 31 March 2023 37.60 1,325 56 For comparability purposes the table below presents dividends per share adjusted for a factor of 1.0811 to reflect the bonus element of the Rights Issue: Pence Impact of Rights Issue Pence Ordinary dividends Final dividend in respect of the year ended 31 March 2024 39.12 (2.93) 36.19 Interim dividend in respect of the year ended 31 March 2024 19.40 (1.46) 17.94 Final dividend in respect of the year ended 31 March 2023 37.60 (2.82) 34.78 The Directors are proposing an interim dividend of 15.84 pence per share to be paid in respect of the year ending 31 March 2025. This would absorb £774 million of shareholders’ equity.

Fair value measurement

Fair value measurement	6 Months Ended
Fair value measurement	Sep. 30, 2024
Fair Value Measurement [Abstract]
Fair value measurement	11. Fair value measurement Assets and liabilities measured at fair value Included in the statement of financial position are certain financial assets and liabilities which are measured at fair value. The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 202 of the Annual Report and Accounts for the year ended 31 March 2024. 30 September 2024 31 March 2024 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 5,589 — 406 5,995 3,084 — 483 3,567 Investments held at fair value through other comprehensive income 1 — 389 — 389 — 397 — 397 Financing derivatives — 467 53 520 — 293 40 333 Commodity contract derivatives — 34 4 38 — 35 — 35 5,589 890 463 6,942 3,084 725 523 4,332 Liabilities Financing derivatives — (1,044) (105) (1,149) — (1,022) (104) (1,126) Commodity contract derivatives — (102) (22) (124) — (105) (13) (118) — (1,146) (127) (1,273) — (1,127) (117) (1,244) Total 5,589 (256) 336 5,669 3,084 (402) 406 3,088 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. The estimated fair value of total borrowings, excluding lease liabilities, using market values at 30 September 2024 is £41,604 million (31 March 2024: £42,617 million). Our level 1 financial investments and liabilities held at fair value are valued using quoted prices from liquid markets and primarily comprise investments in short-term money market funds. Our level 2 financial investments held at fair value primarily include bonds with a tenor greater than one year and are valued using quoted prices for similar instruments in active markets, or quoted prices for identical or similar instruments in inactive markets. Alternatively, they are valued using models where all significant inputs are based directly or indirectly on observable market data. Our level 2 financing derivatives include cross-currency, interest rate and foreign exchange derivatives. We value these derivatives by discounting all future cash flows by externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties. These derivatives can be priced using liquidly traded interest rate curves and foreign exchange rates, and therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 2 commodity derivatives include over-the-counter gas swaps and power swaps as well as forward physical gas deals. We value our contracts based on market data obtained from the New York Mercantile Exchange (NYMEX) and the Intercontinental Exchange (ICE) where forward monthly prices are available. We discount based on externally sourced market yield curves at the reporting date, taking into account the credit quality of both parties and liquidity in the market. Our commodity contracts can be priced using liquidly traded swaps. Therefore we classify our vanilla trades as level 2 under the IFRS 13 framework. Our level 3 financing derivatives include inflation-linked swaps, where the market is illiquid. In valuing these instruments we use in-house valuation models and obtain external valuations to support each reported fair value. Our level 3 commodity contract derivatives primarily consist of our forward purchases of electricity and gas that we value using proprietary models. Derivatives are classified as Level 3 where significant inputs into the valuation technique are neither directly nor indirectly observable (including our own data, which are adjusted, if necessary, to reflect the assumptions market participants would use in the circumstances). 11. Fair value measurement continued Our level 3 investments include equity instruments accounted for at fair value through profit and loss. These equity holdings are part of our corporate venture capital portfolio held by National Grid Partners and comprise a series of relatively small, early-stage non-controlling minority interest unquoted investments where prices or valuation inputs are unobservable. Out of 38 equity investments, 11 are fair valued based on the latest transaction price (a price within the last 12 months), either being the price we paid for the investments, marked to a latest round of funding and adjusted for our preferential rights or based on an internal model. In addition, we have 25 investments without a transaction in the last 12 months that underwent an internal valuation process using the Black-Scholes Murton Option Pricing Model (OPM Backsolve). Between 12 and 18 months a blend between OPM Backsolve and other techniques are utilised such as proxy group revenue multiples, discounted cash flow, comparable company analysis and probability weighted expected return approach in order to triangulate a valuation. After 18 months the valuation is based on these alternative methods as the last fundraising price is no longer a reliable basis for valuation. Our level 3 investments also include our investment in Sunrun Neptune 2016 LLC, which is accounted for at fair value through profit and loss. The investment is fair valued by discounting expected cash flows using a weighted average cost of capital specific to Sunrun Neptune 2016 LLC. The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives Commodity contract derivatives Other Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m 10% increase in commodity prices — — 2 15 — — 10% decrease in commodity prices — — (2) (15) — — +10% market area price change — — 11 12 — — -10% market area price change — — (10) (11) — — +20 basis point increase in Limited Price Index (40) (38) — — — — -20 basis point decrease in LPI market curve 38 38 — — — — +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI) 36 36 — — — — -20 basis point decrease between RPI and CPI market curves (33) (33) — — — — +100 basis points change in discount rate — — — — (6) (8) -100 basis points change in discount rate — — — — 7 9 +10% change in venture capital price — — — — 26 30 -10% change in venture capital price — — — — (26) (30) The impacts disclosed above were considered on a contract by contract basis with the most significant unobservable inputs identified. A reasonably possible change in assumptions for other level 3 assets and liabilities would not result in a material change in fair values. 11. Fair value measurement continued The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2024 2023 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m £m £m At 1 April (64) (100) (13) (36) 483 433 406 297 Net gains/(losses) through the consolidated income statement for the period 2,3 12 25 (19) (4) (54) 26 (61) 47 Purchases — — — (10) 19 11 19 1 Settlements — — 4 7 (42) 3 (38) 10 Reclassification/transfers out of level 3⁴ — — 10 — — — 10 — At 30 September (52) (75) (18) (43) 406 473 336 355 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £12 million (2023: gains of £25 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £19 million (2023: losses of £4 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. £10 million of US Commodity contract derivatives were reclassified out of Level 3 to Level 2 in the period due to improved observability of the fair value of these instruments. The Group also has a number of financial instruments which are not measured at fair value in the balance sheet. The carrying value of current financial assets at amortised cost approximates their fair values, primarily due to short-dated maturities.

Net debt

Net debt	6 Months Ended
Net debt	Sep. 30, 2024
Subclassifications of assets, liabilities and equities [abstract]
Net debt	12. Net debt Net debt is comprised as follows: 30 September 2024 31 March 2024 £m £m Cash and cash equivalents 1,125 559 Current financial investments 6,140 3,699 Borrowings and bank overdrafts (45,176) (47,072) Financing derivatives 1 (629) (793) Net debt (net of related derivative financial instruments) (38,540) (43,607) 1. Includes £58 million liability (31 March 2024: £36 million liability) in relation to the hedging of capital expenditure. The cash flows related to these derivatives are included within investing activities in the consolidated cash flow statement which gives alignment with the presentation of the hedged item. The financing derivatives balance included in net debt exclude the commodity derivatives. The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2024 31 March 2024 Assets Liabilities Total Assets Liabilities Total Financing derivatives 520 (1,149) (629) 333 (1,126) (793) Commodity contract derivatives 38 (124) (86) 35 (118) (83) Total derivative financial instruments 558 (1,273) (715) 368 (1,244) (876)

Pensions and other post-retirem

Pensions and other post-retirement benefit obligations	6 Months Ended
Pensions and other post-retirement benefit obligations	Sep. 30, 2024
Employee Benefits [Abstract]
Pensions and other post-retirement benefit obligations	13. Pensions and other post-retirement benefit obligations 30 September 2024 31 March 2024 £m £m Present value of funded obligations (17,058) (17,601) Fair value of plan assets 19,247 19,733 2,189 2,132 Present value of unfunded obligations (253) (266) Other post-employment liabilities (61) (52) Net defined benefit asset 1,875 1,814 Presented in consolidated statement of financial position: Assets 2,478 2,407 Liabilities (603) (593) 1,875 1,814 Key actuarial assumptions 30 September 2024 31 March 2024 Discount rate – UK past service 5.02 % 4.87 % Discount rate – US 4.90 % 5.15 % Rate of increase in RPI – UK past service 2.95 % 3.05 % The movement in the net pensions and other post-retirement benefit (OPEB) obligations position in the period can be analysed as follows: 30 September 2024 30 September 2023 £m £m Opening net defined benefit asset 1,814 1,951 Cost recognised in the income statement (29) (34) Employer contributions 81 80 Remeasurement and foreign exchange effects recognised in the statement of other comprehensive income 18 (257) Other movements (9) (3) Closing net defined benefit asset 1,875 1,737 The pension and OPEB surpluses in both the UK and the US of £1,359 million and £1,119 million respectively (31 March 2024: £1,317 million and £1,090 million) continue to be recognised as assets under IFRIC 14 as explained on page 180 of the Annual Report and Accounts for the year ended 31 March 2024. In June 2023, the UK High Court issued a ruling, which was subsequently upheld by the Court of Appeal in July 2024, in the case of Virgin Media Limited versus NTL Pension Trustees II Limited and others relating to the validity of certain historical pension changes. The Group has performed its review of past significant changes made to its UK defined benefit pension arrangements and it has concluded that there is no financial impact from the ruling of the case.

Commitments and contingencies

Commitments and contingencies	6 Months Ended
Commitments and contingencies	Sep. 30, 2024
Subclassifications of assets, liabilities and equities [abstract]
Commitments and contingencies	14. Commitments and contingencies At 30 September 2024, there were commitments for future energy purchase agreements of £13,403 million (31 March 2024: £14,175 million) and future capital expenditure contracted but not provided for in relation to the acquisition of property, plant and equipment of £3,697 million (31 March 2024: £3,250 million). We also have contingencies in the form of certain guarantees and letters of credit. These are described in further detail in note 30 to the Annual Report and Accounts for the year ended 31 March 2024. Legal and regulatory proceedings Through the ordinary course of our operations, we are party to various litigation, claims, regulatory proceedings and investigations. We do not expect the ultimate resolution of any proceedings to have a material adverse effect on our results of operations, cash flows or financial position.

Exchange rates

Exchange rates	6 Months Ended
Exchange rates	Sep. 30, 2024
Foreign exchange rates [abstract]
Exchange rates	15. Exchange rates The consolidated results are affected by the exchange rates used to translate the results of our US operations and US dollar transactions. The US dollar to pound sterling exchange rates used were: 30 September 2024 2023 Year ended 31 March 2024 Closing rate applied at period end 1.34 1.22 1.26 Average rate applied for the period 1.30 1.25 1.26

Related party transactions

Related party transactions	6 Months Ended
Related party transactions	Sep. 30, 2024
Related party transactions [abstract]
Related party transactions	16. Related party transactions Related party transactions in the six months ended 30 September 2024 were substantially the same in nature to those disclosed in note 31 of the Annual Report and Accounts for the year ended 31 March 2024. There were no other related party transactions in the period that have materially affected the financial position or performance of the Group.

Post balance sheet events

Post balance sheet events	6 Months Ended
Post balance sheet events	Sep. 30, 2024
Disclosure of non-adjusting events after reporting period [abstract]
Post balance sheet events	17. Post balance sheet events On 1 October 2024, the Group completed the disposal of the ESO (see note 6). The gain on disposal, which is subject to certain completion adjustments, will be reflected in the Annual Report and Accounts for the year ended 31 March 2025.

Basis of preparation and new _2

Basis of preparation and new accounting standards, interpretations and amendments (Policies)	6 Months Ended
	Sep. 30, 2024
Accounting Policies, Changes In Accounting Estimates And Errors [Abstract]
Going concern	Going concern As part of the Directors’ consideration of the appropriateness of adopting the going concern basis of accounting in preparing the half year financial information, the Directors have considered the Group’s principal risks (discussed on page 56) alongside potential downside business cash flow scenarios impacting the Group’s operations. The Directors specifically considered both a base case and a reasonable worst-case scenario for business cash flows. The assessment is prepared on the conservative assumption that the Group has no access to the debt capital markets. The main additional cash flow impacts identified in the reasonable worst-case scenario are: • the timing of the sale of assets classified as held for sale (see note 6); • adverse impacts of higher spend on our capital expenditure programme; • adverse impact from timing across the Group (i.e. a net under-recovery of allowed revenues or reductions in over-collections) and slower collections of outstanding receivables; • higher operating and financing costs than expected; including non-delivery of planned efficiencies across the Group; and • the potential impact of further significant storm costs in the US. As part of their analysis, the Board also considered the following potential levers at their discretion to improve the position identified by the analysis if the debt capital markets are not accessible: • the payment of dividends to shareholders; • significant changes in the phasing of the Group’s capital expenditure programme, with elements of non-essential works and programmes delayed; and • a number of further reductions in operating expenditure across the Group. As at 30 September 2024, the Group had undrawn committed facilities available for general corporate purposes amounting to £7.7 billion. Based on these available liquidity resources and having considered the reasonable worst-case scenario, and the further levers at the Board’s discretion, the Group has not identified any material uncertainties relating to events or conditions that, individually or collectively, may cast significant doubt on its ability to continue as a going concern for the foreseeable future, a period not less than 12 months from the date of this report. In addition to the above, the ability to raise new and extend existing financing was separately included in the analysis, and the Directors noted the c.£1.8 billion of new long-term senior debt issued in the period from 1 April to 30 September 2024 as evidence of the Group’s ability to continue to have access to the debt capital markets if needed. Based on the above, the Directors have concluded the Group is well placed to manage its financing and other business risks satisfactorily, and have a reasonable expectation that the Group will have adequate resources to continue in operation for at least 12 months from the signing date of these consolidated interim financial statements. They therefore consider it appropriate to adopt the going concern basis of accounting in preparing the half year financial information.
New IFRS accounting standards, interpretations and amendments adopted in the period	New IFRS accounting standards, interpretations and amendments adopted in the period
Segment analysis	Revenue and the results of the business are analysed by operating segment, based on the information the Board use internally for the purposes of evaluating the performance of each operating segment and determining resource allocation between them. The Board is National Grid’s chief operating decision maker (as defined by IFRS 8 ‘Operating Segments’) and assesses the profitability of a profit measure that excludes certain income and expenses. We call that measure ‘adjusted profit’. Adjusted profit excludes exceptional items and remeasurements (as defined in note 4) and is used by management to monitor financial performance as it is considered that it aids the comparability of our reported financial performance from year to year. As a matter of course, the Board also considers profitability by segment, excluding the effect of major storms, timing adjustments relating to revenue, certain pass-through costs and deferred tax for our UK Electricity Transmission and UK Electricity Distribution businesses. However, the measure of profit disclosed in this note is operating profit before exceptional items and remeasurements, as this is the measure that is most consistent with the IFRS results reported within these financial statements.
Revenue	Under IFRS 15 ‘Revenue from Contracts with Customers’, revenue is recorded as or when the Group satisfies a performance obligation by transferring a promised good or service to a customer. A good or service is transferred when the customer obtains control of that good or service. The transfer of control of our distribution or transmission services coincides with the use of our network, as electricity and gas pass through our network and reach our customers. The Group principally satisfies its performance obligations over time and the amount of revenue recorded corresponds to the amounts billed and accrued for volumes of gas and electricity delivered/transferred to/from our customers.
Exceptional items and remeasurements	To monitor our segmental financial performance, we use an adjusted consolidated profit measure that excludes certain income and expenses. We exclude items from adjusted profit because, if included, these items could distort understanding of our performance in the period and the comparability between periods. With respect to restructuring and transformation costs, these represent additional expenses incurred that are not related to normal business and day‑to-day activities. These can take place over multiple reporting periods given the scale of the Group, the nature and complexity of the transformation initiatives and due to the impact of strategic transactions. In assessing items to exclude from adjusted profit, management uses an exceptional items framework that has been discussed and approved by the Audit & Risk Committee, as detailed in note 5 of the Annual Report and Accounts for the year ended 31 March 2024. Remeasurements comprise unrealised gains or losses recorded in the consolidated income statement arising from changes in the fair value of certain financial assets and liabilities categorised as held at fair value through profit and loss (FVTPL). Once the fair value movements are realised (for example, when the derivative matures), the previously recognised fair value movements are then reversed through remeasurements and recognised within earnings before exceptional items and remeasurements. These assets and liabilities include commodity contracts and derivative financial instruments to the extent that hedge accounting is either not achieved or is not effective. We have also classified the unrealised gains or losses reported in profit and loss on certain additional assets treated as FVTPL within remeasurements. These relate to financial assets (which fail the ‘solely payments of principal and interest test’ under IFRS 9), the money market fund investments used by Group Treasury for cash management purposes and the net foreign exchange gains and losses on borrowing activities. These are offset by foreign exchange gains and losses on financing derivatives measured at fair value. In all cases, these fair values increase or decrease because of changes in foreign exchange, commodity or other financial indices over which we have no control.
Assets held for sale and discontinued operations	Assets and businesses are classified as held for sale when their carrying amounts are recovered through sale rather than through continuing use. They only meet the held for sale condition when the assets are ready for immediate sale in their present condition, management is committed to the sale and it is highly probable that the sale will complete within one year. Once assets and businesses are classified as held for sale, depreciation and equity accounting ceases and the assets and businesses are remeasured if their carrying value exceeds their fair value less expected costs to sell.
Earnings per share	arnings per share (EPS) calculations are based on profit after tax attributable to equity shareholders of the parent company which excludes non-controlling interests.

Segmental analysis (Tables)

Segmental analysis (Tables)	6 Months Ended
Segmental analysis (Tables)	Sep. 30, 2024
Disclosure of operating segments [abstract]
Schedule of main activities, revenue, operating profit and capital investment by operating segments	The following table describes the main activities for each reportable operating segment: UK Electricity Transmission The high-voltage electricity transmission networks in England and Wales. This includes our Accelerated Strategic Transmission Investment projects to connect more clean, low-carbon power to the transmission network in England and Wales. UK Electricity Distribution The electricity distribution networks of NGED in the East Midlands, West Midlands and South West of England and South Wales. UK Electricity System Operator The Great Britain system operator which is classified as held for sale (see note 6). New England Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New England. New York Gas distribution networks, electricity distribution networks and high-voltage electricity transmission networks in New York. National Grid Ventures Comprises all commercial operations in LNG at the Isle of Grain in the UK (Grain LNG) and Providence, Rhode Island in the US, our electricity generation business in the US, our electricity interconnectors in the UK and our investment in NG Renewables, our renewables business in the US. Whilst NGV operates outside our regulated core business, the electricity interconnectors in the UK are subject to indirect regulation by Ofgem regarding the level of returns they can earn. NG Renewables and Grain LNG were classified as held for sale at 30 September 2024 (see note 6). Revenue Six months ended 30 September 2024 2023 Total sales Sales between segments 1 Sales to third parties Total sales Sales between segments 1 Sales to third £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 1,274 (92) 1,182 1,356 (19) 1,337 UK Electricity Distribution 1,166 (2) 1,164 850 (2) 848 UK Electricity System Operator 1,029 (17) 1,012 1,734 (17) 1,717 New England 1,545 — 1,545 1,441 — 1,441 New York 2,341 — 2,341 2,365 — 2,365 National Grid Ventures 650 (26) 624 666 (27) 639 Other 98 (5) 93 142 — 142 Total revenue from continuing operations 8,103 (142) 7,961 8,554 (65) 8,489 Geographical areas: UK 3,755 4,309 US 4,206 4,180 Total revenue from continuing operations 7,961 8,489 1. Sales between operating segments are priced having regard to the regulatory and legal requirements to which the businesses are subject. The analysis of revenue by geographical area is on the basis of destination. There are no material sales between the UK and US geographical areas. Operating profit/(loss) Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m Operating segments – continuing operations: UK Electricity Transmission 642 839 — (1) 642 838 UK Electricity Distribution 764 476 (5) (4) 759 472 UK Electricity System Operator (364) 443 151 — (213) 443 New England 89 (32) (2) (15) 87 (47) New York (30) (30) (20) 38 (50) 8 National Grid Ventures 147 219 (2) 91 145 310 Other (38) (13) (23) (26) (61) (39) Total operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Geographical areas: UK 1,173 1,956 121 60 1,294 2,016 US 37 (54) (22) 23 15 (31) Total operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Before exceptional items and remeasurements Exceptional items and remeasurements (see note 4) After exceptional items and remeasurements Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m Reconciliation to profit before tax: Operating profit from continuing operations 1,210 1,902 99 83 1,309 1,985 Share of post-tax results of joint ventures and associates 60 59 (3) 12 57 71 Finance income 231 123 3 (8) 234 115 Finance costs (901) (834) (15) 34 (916) (800) Total profit before tax from continuing operations 600 1,250 84 121 684 1,371 2. Segmental analysis continued The following items are included in the total operating profit by segment: Depreciation, amortisation and impairment 30 September 2024 30 September 2023 £m £m Operating segments: UK Electricity Transmission (267) (250) UK Electricity Distribution (122) (105) UK Electricity System Operator — (52) New England (221) (204) New York (351) (321) National Grid Ventures (92) (84) Other (5) (5) Total (1,058) (1,021) Asset type: Property, plant and equipment (936) (868) Non-current intangible assets (122) (153) Total (1,058) (1,021) Capital investment represents additions to property, plant and equipment, prepayments to suppliers to secure production capacity in relation to our capital projects, non-current intangibles and additional equity investments in joint ventures and associates. Segmental information used for internal decision making was revised in the year ended 31 March 2024 to include capital expenditure prepayments and additional equity investments in joint ventures and associates. Capital investments exclude additions for assets or businesses from the point they are classified as held for sale. 30 September 2024 30 September 2023¹ £m £m Operating segments: UK Electricity Transmission 1,290 899 UK Electricity Distribution 647 608 UK Electricity System Operator — 75 New England 814 789 New York 1,569 1,257 National Grid Ventures 279 316 Other 4 2 Total 4,603 3,946 Asset type: Property, plant and equipment 4,200 3,413 Non-current intangible assets 196 257 Equity investments in joint ventures and associates 102 151 Capital expenditure prepayments 105 125 Total 4,603 3,946 1. Comparative amounts have been represented to reflect the change in presentation for capital investments.
Schedule of geographical analysis of non-current assets	30 September 2024 31 March 2024 £m £m Split by geographical area: UK 40,738 40,065 US 42,968 44,270 Total 83,706 84,335 Reconciliation to total non-current assets: Pension assets 2,478 2,407 Financial and other investments 795 880 Derivative financial assets 413 324 Non-current assets 87,392 87,946

Revenue (Tables)

Revenue (Tables)	6 Months Ended
Revenue (Tables)	Sep. 30, 2024
Revenue [abstract]
Schedule of disaggregation of revenue from contracts with customers	Revenue for the six months ended 30 September 2024 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New New National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,116 — 46 46 126 430 — 1,764 Distribution — 1,113 — 1,468 2,181 — 1 4,763 System Operator — — 966 — — — — 966 Other 1 16 49 — 4 8 43 — 120 Total IFRS 15 revenue 1,132 1,162 1,012 1,518 2,315 473 1 7,613 Other revenue Generation — — — — — 191 — 191 Other 2 50 2 — 27 26 (40) 92 157 Total other revenue 50 2 — 27 26 151 92 348 Total revenue from continuing operations 1,182 1,164 1,012 1,545 2,341 624 93 7,961 Geographic split of revenue for the six months ended 30 September 2024 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New National Grid Ventures Other Total Revenue under IFRS 15 UK 1,132 1,162 1,012 — — 430 — 3,736 US — — — 1,518 2,315 43 1 3,877 Total IFRS 15 revenue 1,132 1,162 1,012 1,518 2,315 473 1 7,613 Other revenue UK 50 2 — — — (38) 5 19 US — — — 27 26 189 87 329 Total other revenue 50 2 — 27 26 151 92 348 Total revenue from continuing operations 1,182 1,164 1,012 1,545 2,341 624 93 7,961 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated by NG Renewables which was classified as held for sale in the period (see note 6). 2. Other revenue, recognised in accordance with accounting standards other than IFRS 15, includes property sales by our UK commercial property business, net fair value gains and losses in respect of investments in our National Grid Partners business, rental income, income arising in connection with the Transition Services Agreements in place following the sales of NECO and the UK Gas Transmission businesses and the planned sale of the ESO, and an adjustment to NGV revenue in respect of the interconnector cap and floor and Use of Revenue regimes constructed by Ofgem. Revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures Other Total Revenue under IFRS 15 Transmission 1,299 — 5 43 283 426 — 2,056 Distribution — 810 — 1,329 2,047 — — 4,186 System Operator — — 1,712 — — — — 1,712 Other 1 9 36 — 4 7 75 — 131 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue Generation — — — — — 181 — 181 Other 2 29 2 — 65 28 (43) 142 223 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 Geographic split of revenue for the six months ended 30 September 2023 UK Electricity Transmission UK Electricity Distribution UK Electricity System Operator New England New York National Grid Ventures Other Total Revenue under IFRS 15 UK 1,308 846 1,717 — — 430 — 4,301 US — — — 1,376 2,337 71 — 3,784 Total IFRS 15 revenue 1,308 846 1,717 1,376 2,337 501 — 8,085 Other revenue UK 29 2 — — — (50) 27 8 US — — — 65 28 188 115 396 Total other revenue 29 2 — 65 28 138 142 404 Total revenue from continuing operations 1,337 848 1,717 1,441 2,365 639 142 8,489 1. The UK Electricity Transmission and UK Electricity Distribution other IFRS 15 revenue principally relates to engineering recharges, which are the recovery of costs incurred for construction work requested by customers, such as the re-routing of existing network assets. Within NGV, the other IFRS 15 revenue principally relates to revenue generated by NG Renewables. 2.

Exceptional items and remeasu_2

Exceptional items and remeasurements (Tables)	6 Months Ended
Exceptional items and remeasurements (Tables)	Sep. 30, 2024
Exceptional Items And Remeasurements [Abstract]
Schedule of exceptional items and remeasurements from continuing operations	Six months ended 30 September 2024 Exceptional items Remeasurements Total Included within operating profit from continuing operations Provision for UK electricity balancing costs 151 — 151 Major transformation programme (42) — (42) Changes in environmental provisions (1) — (1) Net losses on commodity contract derivatives — (9) (9) 108 (9) 99 Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations Cost efficiency programme (39) — (39) Transaction, separation and integration costs 1 (11) — (11) IFA1 fire insurance proceeds 92 — 92 Net gains on commodity contract derivatives — 41 41 42 41 83 1. Transaction, separation and integration costs represent the aggregate of distinct activities undertaken by the Group. Details of remeasurements, tax exceptional items and the tax effect of exceptional items and remeasurements are also provided in this note. Six months ended 30 September 2024 Exceptional items Remeasurements Total Included within operating profit from continuing operations 108 (9) 99 Included within net finance costs (note 5) Net losses on derivative financial instruments — (15) (15) Net gains on financial assets at fair value through profit and loss — 3 3 — (12) (12) Included within share of post-tax results of joint ventures and associates Net losses on financial instruments — (3) (3) — (3) (3) Total included within profit before tax from continuing operations 108 (24) 84 Tax on exceptional items and remeasurements 11 6 17 Total exceptional items and remeasurements after tax from 119 (18) 101 Six months ended 30 September 2023 Exceptional items Remeasurements Total Included within operating profit from continuing operations 42 41 83 Included within net finance costs (note 5) Net gains on derivative financial instruments — 34 34 Net losses on financial assets at fair value through profit and loss — (8) (8) — 26 26 Included within share of post-tax results of joint ventures and associates Net gains on financial instruments — 12 12 — 12 12 Total included within profit before tax from continuing operations 42 79 121 Tax on exceptional items and remeasurements 1 (21) (20) Total exceptional items and remeasurements after tax from 43 58 101

Finance income and costs (Table

Finance income and costs (Tables)	6 Months Ended
Finance income and costs (Tables)	Sep. 30, 2024
Analysis of income and expense [abstract]
Schedule of finance income and costs	2024 2023 Six months ended 30 September £m £m Finance income Interest income from financing activities 143 52 Net interest on pensions and other post-retirement benefit obligations 50 51 Net gains/(losses) on financial assets at fair value through profit and loss 3 (8) Other interest income 38 20 234 115 Finance costs Interest expense on financial instruments 1 (950) (903) Unwinding of discount on provisions and other liabilities (64) (50) Other interest (21) (8) Net (losses)/gains on derivative financial instruments 2 (15) 34 Less: interest capitalised 3 134 127 (916) (800) Net finance costs from continuing operations (682) (685) 1. Finance costs include principal accretion on inflation-linked debt of £87 million (2023: £149 million) and income related to principal accretion on inflation-linked swaps of £4 million (2023: £18 million expense). 2. Includes a net foreign exchange gain on borrowing activities, offset by foreign exchange gains and losses on financing derivatives measured at fair value. 3. Interest on funding attributable to assets in the course of construction in the current period was capitalised at a rate of 4.3% (2023: 4.7%). In the UK, capitalised interest qualifies for a current year tax deduction with tax relief claimed of £16 million (2023: £21 million). In the US, capitalised interest is added to the cost of property, plant and equipment and qualifies for tax depreciation allowances.

Assets held for sale and disc_2

Assets held for sale and discontinued operations (Tables)	6 Months Ended
Assets held for sale and discontinued operations (Tables)	Sep. 30, 2024
Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract]
Schedule of assets and liabilities classified as held for sale	The following assets and liabilities were classified as held for sale: 30 September 2024 31 March 2024 Total assets Total liabilities held for sale Net assets/(liabilities) held for sale £m Total assets Total liabilities held for sale Net assets/(liabilities) held for sale £m UK Electricity System Operator 1,549 (992) 557 1,134 (1,427) (293) National Grid Renewables 1,146 (10) 1,136 — — — Grain LNG 1,036 (307) 729 — — — Investment in GasT TopCo Limited — — — 689 — 689 RAA — — — — (47) (47) Net assets/(liabilities) held for sale 3,731 (1,309) 2,422 1,823 (1,474) 349 The following assets and liabilities of the ESO were classified as held for sale at 30 September 2024. £m Intangible assets 485 Property, plant and equipment 121 Trade and other receivables 375 Pension asset 16 Cash and cash equivalents 51 Financial investments 501 Total assets 1,549 Borrowings (13) Other liabilities (632) Provision for UK electricity balancing costs (347) Total liabilities (992) Net assets 557 The following assets and liabilities were classified as held for sale at 30 September 2024. National Grid Renewables Grain LNG £m £m Goodwill 80 — Other intangible assets — 5 Property, plant and equipment 90 856 Investments in joint ventures and associates 704 — Trade and other receivables 74 47 Cash and cash equivalents 39 106 Financial investments 23 — Other assets 136 22 Total assets 1,146 1,036 Borrowings (2) (120) Other liabilities (8) (187) Total liabilities (10) (307) Net assets 1,136 729
Summary of discontinued operations	The summary income statements for the periods ended 30 September 2024 and 2023 are as follows: 2024 2023 £m £m Operating profit — — Finance income 5 9 Finance costs 1 47 61 Profit before tax 52 70 Tax (1) (5) Profit after tax from discontinued operations 51 65 Gain on disposal 25 — Total profit after tax from discontinued operations 76 65 1. Finance costs include the remeasurement of the FAA option, the FAA forward and the RAA. The summary statements of comprehensive income are as follows: 2024 2023 £m £m Profit after tax from discontinued operations 76 65 Other comprehensive (loss)/income from discontinued operations Items from discontinued operations that may be reclassified subsequently to profit or loss: Net losses on investments in debt instruments measured at fair value through other (13) (12) Tax on items that may be reclassified subsequently to profit or loss 3 3 Total losses from discontinued operations that may be reclassified subsequently to profit or loss (10) (9) Other comprehensive loss for the period, net of tax, from discontinued operations (10) (9) Total comprehensive income for the period from discontinued operations 66 56

Earnings per share (Tables)

Earnings per share (Tables)	6 Months Ended
Earnings per share (Tables)	Sep. 30, 2024
Earnings per share [abstract]
Schedule of basic and diluted earnings per share	Basic earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2024 2024 2023 2023¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 571 12.6 1,063 26.7 Profit after tax from discontinued operations attributable to the parent 76 1.7 65 1.6 Total profit after tax attributable to the parent 647 14.3 1,128 28.3 2024 2023¹ millions millions Weighted average number of shares – basic 4,526 3,981 1. Comparative amounts have been restated to reflect the impact of the bonus element of the Rights Issue (see note 9). (b) Diluted earnings per share Earnings EPS Earnings EPS Six months ended 30 September 2024 2024 2023 2023¹ £m pence £m pence Profit after tax from continuing operations attributable to the parent 571 12.6 1,063 26.6 Profit after tax from discontinued operations attributable to the parent 76 1.6 65 1.6 Total profit after tax attributable to the parent 647 14.2 1,128 28.2 2024 2023¹ millions millions Weighted average number of shares – diluted 4,547 3,999 1. Comparative amounts have been restated to reflect the impact of the bonus element of the Rights Issue (see note 9).

Rights Issue (Tables)

Rights Issue (Tables)	6 Months Ended
Rights Issue (Tables)	Sep. 30, 2024
Issued capital [abstract]
Schedule of share capital	Allotted, called up and fully paid shares of 12 204 ⁄ 473 pence each: Allotted, called-up and fully paid Shares Nominal value million £m At 1 April 2024 3,967 493 Issued in Rights Issue 1,085 135 Issued during the period in lieu of dividends 1 74 9 At 30 September 2024 2 5,126 637 1. The issue of shares under the scrip dividend programme is considered to be a bonus issue under the terms of the Companies Act 2006, and the nominal value of the shares is charged to the share premium account. 2. At 30 September 2024, the Company held 241 million (31 March 2024: 247 million) of its own shares.

Dividends (Tables)

Dividends (Tables)	6 Months Ended
Dividends (Tables)	Sep. 30, 2024
Subclassifications of assets, liabilities and equities [abstract]
Schedule of dividends	Pence Cash Scrip Ordinary dividends Final dividend in respect of the year ended 31 March 2024 39.12 811 643 Interim dividend in respect of the year ended 31 March 2024 19.40 393 320 Final dividend in respect of the year ended 31 March 2023 37.60 1,325 56 For comparability purposes the table below presents dividends per share adjusted for a factor of 1.0811 to reflect the bonus element of the Rights Issue: Pence Impact of Rights Issue Pence Ordinary dividends Final dividend in respect of the year ended 31 March 2024 39.12 (2.93) 36.19 Interim dividend in respect of the year ended 31 March 2024 19.40 (1.46) 17.94 Final dividend in respect of the year ended 31 March 2023 37.60 (2.82) 34.78

Fair value measurement (Tables)

Fair value measurement (Tables)	6 Months Ended
Fair value measurement (Tables)	Sep. 30, 2024
Fair Value Measurement [Abstract]
Schedule of fair value measurement of assets	The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 202 of the Annual Report and Accounts for the year ended 31 March 2024. 30 September 2024 31 March 2024 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 5,589 — 406 5,995 3,084 — 483 3,567 Investments held at fair value through other comprehensive income 1 — 389 — 389 — 397 — 397 Financing derivatives — 467 53 520 — 293 40 333 Commodity contract derivatives — 34 4 38 — 35 — 35 5,589 890 463 6,942 3,084 725 523 4,332 Liabilities Financing derivatives — (1,044) (105) (1,149) — (1,022) (104) (1,126) Commodity contract derivatives — (102) (22) (124) — (105) (13) (118) — (1,146) (127) (1,273) — (1,127) (117) (1,244) Total 5,589 (256) 336 5,669 3,084 (402) 406 3,088 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2024 2023 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m £m £m At 1 April (64) (100) (13) (36) 483 433 406 297 Net gains/(losses) through the consolidated income statement for the period 2,3 12 25 (19) (4) (54) 26 (61) 47 Purchases — — — (10) 19 11 19 1 Settlements — — 4 7 (42) 3 (38) 10 Reclassification/transfers out of level 3⁴ — — 10 — — — 10 — At 30 September (52) (75) (18) (43) 406 473 336 355 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £12 million (2023: gains of £25 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £19 million (2023: losses of £4 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. £10 million of US Commodity contract derivatives were reclassified out of Level 3 to Level 2 in the period due to improved observability of the fair value of these instruments.
Schedule of fair value measurement of liabilities	The following table categorises these assets and liabilities by the valuation methodology applied in determining their fair value using the fair value hierarchy described on page 202 of the Annual Report and Accounts for the year ended 31 March 2024. 30 September 2024 31 March 2024 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Investments held at fair value through profit and loss 5,589 — 406 5,995 3,084 — 483 3,567 Investments held at fair value through other comprehensive income 1 — 389 — 389 — 397 — 397 Financing derivatives — 467 53 520 — 293 40 333 Commodity contract derivatives — 34 4 38 — 35 — 35 5,589 890 463 6,942 3,084 725 523 4,332 Liabilities Financing derivatives — (1,044) (105) (1,149) — (1,022) (104) (1,126) Commodity contract derivatives — (102) (22) (124) — (105) (13) (118) — (1,146) (127) (1,273) — (1,127) (117) (1,244) Total 5,589 (256) 336 5,669 3,084 (402) 406 3,088 1. Investments held include instruments which meet the criteria of IFRS 9 or IAS 19. The changes in fair value of our level 3 financial assets and liabilities in the six months to 30 September are presented below: Financing derivatives Commodity contract derivatives Other 1 Total 2024 2023 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m £m £m At 1 April (64) (100) (13) (36) 483 433 406 297 Net gains/(losses) through the consolidated income statement for the period 2,3 12 25 (19) (4) (54) 26 (61) 47 Purchases — — — (10) 19 11 19 1 Settlements — — 4 7 (42) 3 (38) 10 Reclassification/transfers out of level 3⁴ — — 10 — — — 10 — At 30 September (52) (75) (18) (43) 406 473 336 355 1. Other comprises our investments in Sunrun Neptune 2016 LLC and the investments made by National Grid Partners, which are accounted for at fair value through profit and loss. Net gains and loss are recognised within finance income and costs in the income statement. 2. Gains of £12 million (2023: gains of £25 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the income statement. 3. Losses of £19 million (2023: losses of £4 million) are attributable to the commodity contract derivative financial instruments held at the end of the reporting period and have been recognised in other operating costs in the consolidated income statement. 4. £10 million of US Commodity contract derivatives were reclassified out of Level 3 to Level 2 in the period due to improved observability of the fair value of these instruments.
Schedule of impacts of reasonably possible changes in significant Level 3 assumptions	The impacts on a post-tax basis of reasonably possible changes in significant assumptions used in valuing assets and liabilities classified within level 3 of the fair value hierarchy are as follows: Financing derivatives Commodity contract derivatives Other Six months ended 30 September 2024 2023 2024 2023 2024 2023 £m £m £m £m £m £m 10% increase in commodity prices — — 2 15 — — 10% decrease in commodity prices — — (2) (15) — — +10% market area price change — — 11 12 — — -10% market area price change — — (10) (11) — — +20 basis point increase in Limited Price Index (40) (38) — — — — -20 basis point decrease in LPI market curve 38 38 — — — — +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI) 36 36 — — — — -20 basis point decrease between RPI and CPI market curves (33) (33) — — — — +100 basis points change in discount rate — — — — (6) (8) -100 basis points change in discount rate — — — — 7 9 +10% change in venture capital price — — — — 26 30 -10% change in venture capital price — — — — (26) (30)

Net debt (Tables)

Net debt (Tables)	6 Months Ended
Net debt (Tables)	Sep. 30, 2024
Subclassifications of assets, liabilities and equities [abstract]
Schedule of components of net debt	Net debt is comprised as follows: 30 September 2024 31 March 2024 £m £m Cash and cash equivalents 1,125 559 Current financial investments 6,140 3,699 Borrowings and bank overdrafts (45,176) (47,072) Financing derivatives 1 (629) (793) Net debt (net of related derivative financial instruments) (38,540) (43,607) 1. Includes £58 million liability (31 March 2024: £36 million liability) in relation to the hedging of capital expenditure. The cash flows related to these derivatives are included within investing activities in the consolidated cash flow statement which gives alignment with the presentation of the hedged item. The financing derivatives balance included in net debt exclude the commodity derivatives.
Schedule of balance sheet allocation of derivative balances	The following table splits out the total derivative balances on the face of the consolidated statement of financial position by category: 30 September 2024 31 March 2024 Assets Liabilities Total Assets Liabilities Total Financing derivatives 520 (1,149) (629) 333 (1,126) (793) Commodity contract derivatives 38 (124) (86) 35 (118) (83) Total derivative financial instruments 558 (1,273) (715) 368 (1,244) (876)

Pensions and other post-retir_2

Pensions and other post-retirement benefit obligations (Tables)	6 Months Ended
	Sep. 30, 2024
Employee Benefits [Abstract]
Schedule of defined benefit plan recognised in balance sheet	30 September 2024 31 March 2024 £m £m Present value of funded obligations (17,058) (17,601) Fair value of plan assets 19,247 19,733 2,189 2,132 Present value of unfunded obligations (253) (266) Other post-employment liabilities (61) (52) Net defined benefit asset 1,875 1,814 Presented in consolidated statement of financial position: Assets 2,478 2,407 Liabilities (603) (593) 1,875 1,814
Schedule of key actuarial assumptions	Key actuarial assumptions 30 September 2024 31 March 2024 Discount rate – UK past service 5.02 % 4.87 % Discount rate – US 4.90 % 5.15 % Rate of increase in RPI – UK past service 2.95 % 3.05 %
Schedule of reconciliation of the net defined benefit asset	The movement in the net pensions and other post-retirement benefit (OPEB) obligations position in the period can be analysed as follows: 30 September 2024 30 September 2023 £m £m Opening net defined benefit asset 1,814 1,951 Cost recognised in the income statement (29) (34) Employer contributions 81 80 Remeasurement and foreign exchange effects recognised in the statement of other comprehensive income 18 (257) Other movements (9) (3) Closing net defined benefit asset 1,875 1,737

Exchange rates (Tables)

Exchange rates (Tables)	6 Months Ended
Exchange rates (Tables)	Sep. 30, 2024
Foreign exchange rates [abstract]
Schedule of average and closing foreign exchange rates	The US dollar to pound sterling exchange rates used were: 30 September 2024 2023 Year ended 31 March 2024 Closing rate applied at period end 1.34 1.22 1.26 Average rate applied for the period 1.30 1.25 1.26

Basis of preparation and new _3

Basis of preparation and new accounting standards, interpretations and amendments (Details) - GBP (£) £ in Billions	Mar. 11, 2024	Jan. 31, 2023	Sep. 30, 2024
Disclosure of detailed information about borrowings [line items]
Undrawn borrowing facilities			£ 7.7
GasT TopCo Limited
Disclosure of detailed information about borrowings [line items]
Proportion of ownership interest in associate	20%	40%
Fixed interest rate bonds
Disclosure of detailed information about borrowings [line items]
Notional amount			£ 1.8

Segmental analysis - Narrative

Segmental analysis - Narrative (Details)	Sep. 30, 2024 segment
Disclosure of operating segments [abstract]
Number of reportable operating segments	6

Segmental analysis - Schedule o

Segmental analysis - Schedule of revenue by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of operating segments [line items]
Total revenue from continuing operations	£ 7,961	£ 8,489
UK
Disclosure of operating segments [line items]
Total revenue from continuing operations	3,755	4,309
US
Disclosure of operating segments [line items]
Total revenue from continuing operations	4,206	4,180
UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,182	1,337
UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,164	848
UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,012	1,717
New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,545	1,441
New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	2,341	2,365
National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	624	639
Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	93	142
Operating segments
Disclosure of operating segments [line items]
Total revenue from continuing operations	8,103	8,554
Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,274	1,356
Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,166	850
Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,029	1,734
Operating segments \| New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	1,545	1,441
Operating segments \| New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	2,341	2,365
Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	650	666
Operating segments \| Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	98	142
Sales between segments
Disclosure of operating segments [line items]
Total revenue from continuing operations	(142)	(65)
Sales between segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Total revenue from continuing operations	(92)	(19)
Sales between segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Total revenue from continuing operations	(2)	(2)
Sales between segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Total revenue from continuing operations	(17)	(17)
Sales between segments \| New England
Disclosure of operating segments [line items]
Total revenue from continuing operations	0	0
Sales between segments \| New York
Disclosure of operating segments [line items]
Total revenue from continuing operations	0	0
Sales between segments \| National Grid Ventures
Disclosure of operating segments [line items]
Total revenue from continuing operations	(26)	(27)
Sales between segments \| Other
Disclosure of operating segments [line items]
Total revenue from continuing operations	£ (5)	£ 0

Segmental analysis - Schedule_2

Segmental analysis - Schedule of operating profit/(loss) by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ 1,309	£ 1,985
Share of post-tax results of joint ventures and associates	57	71
Finance income	234	115
Finance costs	(916)	(800)
Profit before tax	684	1,371
UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,294	2,016
US
Disclosure of operating segments [line items]
Operating profit from continuing operations	15	(31)
Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	642	838
Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	759	472
Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	(213)	443
Operating segments \| New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	87	(47)
Operating segments \| New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	(50)	8
Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	145	310
Operating segments \| Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	(61)	(39)
Before exceptional items and remeasurements
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,210	1,902
Share of post-tax results of joint ventures and associates	60	59
Finance income	231	123
Finance costs	(901)	(834)
Profit before tax	600	1,250
Before exceptional items and remeasurements \| UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	1,173	1,956
Before exceptional items and remeasurements \| US
Disclosure of operating segments [line items]
Operating profit from continuing operations	37	(54)
Before exceptional items and remeasurements \| Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	642	839
Before exceptional items and remeasurements \| Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	764	476
Before exceptional items and remeasurements \| Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	(364)	443
Before exceptional items and remeasurements \| Operating segments \| New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	89	(32)
Before exceptional items and remeasurements \| Operating segments \| New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	(30)	(30)
Before exceptional items and remeasurements \| Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	147	219
Before exceptional items and remeasurements \| Operating segments \| Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	(38)	(13)
Exceptional items and remeasurements
Disclosure of operating segments [line items]
Operating profit from continuing operations	99	83
Share of post-tax results of joint ventures and associates	(3)	12
Finance income	3	(8)
Finance costs	(15)	34
Profit before tax	84	121
Exceptional items and remeasurements \| UK
Disclosure of operating segments [line items]
Operating profit from continuing operations	121	60
Exceptional items and remeasurements \| US
Disclosure of operating segments [line items]
Operating profit from continuing operations	(22)	23
Exceptional items and remeasurements \| Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Operating profit from continuing operations	0	(1)
Exceptional items and remeasurements \| Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Operating profit from continuing operations	(5)	(4)
Exceptional items and remeasurements \| Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Operating profit from continuing operations	151	0
Exceptional items and remeasurements \| Operating segments \| New England
Disclosure of operating segments [line items]
Operating profit from continuing operations	(2)	(15)
Exceptional items and remeasurements \| Operating segments \| New York
Disclosure of operating segments [line items]
Operating profit from continuing operations	(20)	38
Exceptional items and remeasurements \| Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Operating profit from continuing operations	(2)	91
Exceptional items and remeasurements \| Operating segments \| Other
Disclosure of operating segments [line items]
Operating profit from continuing operations	£ (23)	£ (26)

Segmental analysis - Schedule_3

Segmental analysis - Schedule of depreciation, amortisation and impairment by operating segments (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	£ (1,058)	£ (1,021)
Property, plant and equipment
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(936)	(868)
Non-current intangible assets
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(122)	(153)
Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(267)	(250)
Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(122)	(105)
Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	0	(52)
Operating segments \| New England
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(221)	(204)
Operating segments \| New York
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(351)	(321)
Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	(92)	(84)
Operating segments \| Other
Disclosure of operating segments [line items]
Depreciation, amortisation and impairment loss	£ (5)	£ (5)

Segmental analysis - Schedule_4

Segmental analysis - Schedule of capital investment by segment (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of operating segments [line items]
Capital investment	£ 4,603	£ 3,946
Operating segments \| UK Electricity Transmission
Disclosure of operating segments [line items]
Capital investment	1,290	899
Operating segments \| UK Electricity Distribution
Disclosure of operating segments [line items]
Capital investment	647	608
Operating segments \| UK Electricity System Operator
Disclosure of operating segments [line items]
Capital investment	0	75
Operating segments \| New England
Disclosure of operating segments [line items]
Capital investment	814	789
Operating segments \| New York
Disclosure of operating segments [line items]
Capital investment	1,569	1,257
Operating segments \| National Grid Ventures
Disclosure of operating segments [line items]
Capital investment	279	316
Operating segments \| Other
Disclosure of operating segments [line items]
Capital investment	4	2
Property, plant and equipment
Disclosure of operating segments [line items]
Capital investment	4,200	3,413
Non-current intangible assets
Disclosure of operating segments [line items]
Capital investment	196	257
Equity investments in joint ventures and associates
Disclosure of operating segments [line items]
Capital investment	102	151
Capital expenditure prepayments
Disclosure of operating segments [line items]
Capital investment	£ 105	£ 125

Segmental analysis - Schedule_5

Segmental analysis - Schedule of geographical analysis of non-current assets (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure of operating segments [line items]
Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts	£ 83,706	£ 84,335
Pension assets	2,478	2,407
Financial and other investments	795	880
Derivative financial assets	413	324
Total non-current assets	87,392	87,946
UK
Disclosure of operating segments [line items]
Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts	40,738	40,065
US
Disclosure of operating segments [line items]
Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts	£ 42,968	£ 44,270

Revenue (Details)

Revenue (Details) - GBP (£) £ in Millions	6 Months Ended
Revenue (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Sep. 30, 2023
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	£ 7,613	£ 8,085
Total other revenue	348	404
Total revenue from continuing operations	7,961	8,489
UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	3,736	4,301
Total other revenue	19	8
Total revenue from continuing operations	3,755	4,309
US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	3,877	3,784
Total other revenue	329	396
Total revenue from continuing operations	4,206	4,180
UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,132	1,308
Total other revenue	50	29
Total revenue from continuing operations	1,182	1,337
UK Electricity Transmission \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,132	1,308
Total other revenue	50	29
UK Electricity Transmission \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,162	846
Total other revenue	2	2
Total revenue from continuing operations	1,164	848
UK Electricity Distribution \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,162	846
Total other revenue	2	2
UK Electricity Distribution \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,012	1,717
Total other revenue	0	0
Total revenue from continuing operations	1,012	1,717
UK Electricity System Operator \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,012	1,717
Total other revenue	0	0
UK Electricity System Operator \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,518	1,376
Total other revenue	27	65
Total revenue from continuing operations	1,545	1,441
New England \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New England \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,518	1,376
Total other revenue	27	65
New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,315	2,337
Total other revenue	26	28
Total revenue from continuing operations	2,341	2,365
New York \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
New York \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,315	2,337
Total other revenue	26	28
National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	473	501
Total other revenue	151	138
Total revenue from continuing operations	624	639
National Grid Ventures \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	430	430
Total other revenue	(38)	(50)
National Grid Ventures \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	43	71
Total other revenue	189	188
Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1	0
Total other revenue	92	142
Total revenue from continuing operations	93	142
Other \| UK
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	5	27
Other \| US
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1	0
Total other revenue	87	115
Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,764	2,056
Transmission \| UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,116	1,299
Transmission \| UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Transmission \| UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	46	5
Transmission \| New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	46	43
Transmission \| New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	126	283
Transmission \| National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	430	426
Transmission \| Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	4,763	4,186
Distribution \| UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution \| UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,113	810
Distribution \| UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution \| New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1,468	1,329
Distribution \| New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	2,181	2,047
Distribution \| National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Distribution \| Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	1	0
System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	966	1,712
System Operator \| UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator \| UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator \| UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	966	1,712
System Operator \| New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator \| New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator \| National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
System Operator \| Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Generation
Revenue from Contracts with Customers [line items]
Total other revenue	191	181
Generation \| UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation \| UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation \| UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation \| New England
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation \| New York
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Generation \| National Grid Ventures
Revenue from Contracts with Customers [line items]
Total other revenue	191	181
Generation \| Other
Revenue from Contracts with Customers [line items]
Total other revenue	0	0
Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	120	131
Total other revenue	157	223
Other \| UK Electricity Transmission
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	16	9
Total other revenue	50	29
Other \| UK Electricity Distribution
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	49	36
Total other revenue	2	2
Other \| UK Electricity System Operator
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	0	0
Other \| New England
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	4	4
Total other revenue	27	65
Other \| New York
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	8	7
Total other revenue	26	28
Other \| National Grid Ventures
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	43	75
Total other revenue	(40)	(43)
Other \| Other
Revenue from Contracts with Customers [line items]
Total IFRS 15 revenue	0	0
Total other revenue	£ 92	£ 142

Exceptional items and remeasu_3

Exceptional items and remeasurements - Schedule of exceptional items and remeasurements from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended		12 Months Ended	29 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024	Mar. 31, 2024
Included within operating profit from continuing operations
Operating profit	£ 1,309	£ 1,985
Included within net finance costs
Net (losses) gains on derivative financial instruments	(15)	34
Net gains/(losses) on financial assets at fair value through profit and loss	3	(8)
Net finance costs	(682)	(685)
Included within share of post-tax results of joint ventures and associates
Share of post-tax results of joint ventures and associates	57	71
Profit before tax	684	1,371
Tax on exceptional items and remeasurements	(112)	(307)
Profit after tax from continuing operations	572	1,064
Exceptional items and remeasurements
Included within operating profit from continuing operations
Provision for UK electricity balancing costs	151
Major transformation/cost efficiency programme	(42)	(39)
Changes in environmental provisions	(1)
Transaction, separation and integration costs		(11)
IFA1 fire insurance proceeds		92
Net (losses) gains on commodity contract derivatives	(9)	41
Operating profit	99	83
Included within net finance costs
Net (losses) gains on derivative financial instruments	(15)	34
Net gains/(losses) on financial assets at fair value through profit and loss	3	(8)
Net finance costs	(12)	26
Included within share of post-tax results of joint ventures and associates
Net (losses) gains on financial instruments	(3)	12
Share of post-tax results of joint ventures and associates	(3)	12
Profit before tax	84	121
Tax on exceptional items and remeasurements	17	(20)
Profit after tax from continuing operations	101	101
Exceptional items
Included within operating profit from continuing operations
Provision for UK electricity balancing costs	151		£ (498)
Major transformation/cost efficiency programme	(42)	(39)		£ (207)
Changes in environmental provisions	(1)
Transaction, separation and integration costs		(11)
IFA1 fire insurance proceeds		92
Net (losses) gains on commodity contract derivatives	0	0
Operating profit	108	42
Included within net finance costs
Net (losses) gains on derivative financial instruments	0	0
Net gains/(losses) on financial assets at fair value through profit and loss	0	0
Net finance costs	0	0
Included within share of post-tax results of joint ventures and associates
Net (losses) gains on financial instruments	0	0
Share of post-tax results of joint ventures and associates	0	0
Profit before tax	108	42
Tax on exceptional items and remeasurements	11	1
Profit after tax from continuing operations	119	43
Remeasurements
Included within operating profit from continuing operations
Provision for UK electricity balancing costs	0
Major transformation/cost efficiency programme	0	0
Changes in environmental provisions	0
Transaction, separation and integration costs		0
IFA1 fire insurance proceeds		0
Net (losses) gains on commodity contract derivatives	(9)	41
Operating profit	(9)	41
Included within net finance costs
Net (losses) gains on derivative financial instruments	(15)	34
Net gains/(losses) on financial assets at fair value through profit and loss	3	(8)
Net finance costs	(12)	26
Included within share of post-tax results of joint ventures and associates
Net (losses) gains on financial instruments	(3)	12
Share of post-tax results of joint ventures and associates	(3)	12
Profit before tax	(24)	79
Tax on exceptional items and remeasurements	6	(21)
Profit after tax from continuing operations	£ (18)	£ 58

Exceptional items and remeasu_4

Exceptional items and remeasurements - Narrative (Details) - GBP (£) £ in Millions	1 Months Ended	6 Months Ended		12 Months Ended	29 Months Ended
	Nov. 30, 2021	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024	Mar. 31, 2024
Disclosure Of Exceptional Items [Line Items]
Major transformation programme, period		4 years
Cost efficiency programme, annual savings target	£ 400
Cost efficiency programme, period	3 years
Exceptional items
Disclosure Of Exceptional Items [Line Items]
Provision for UK electricity balancing costs		£ (151)		£ 498
Expense of restructuring activities		42	£ 39		£ 207
Cash outflows relating to restructuring activities			28
Changes in environmental provisions		1
Transaction, separation and integration costs			11
Cash outflows relating to transaction, separation and integration costs			9
Income from insurance recovery			92
Cash inflows relating to insurance recovery			£ 0
Exceptional items \| Major transformation programme
Disclosure Of Exceptional Items [Line Items]
Expense of restructuring activities		42
Cash outflows relating to restructuring activities		£ 33

Finance income and costs (Detai

Finance income and costs (Details) - GBP (£) £ in Millions	6 Months Ended
Finance income and costs (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Sep. 30, 2023
Finance income
Interest income from financing activities	£ 143	£ 52
Net interest on pensions and other post-retirement benefit obligations	50	51
Net gains/(losses) on financial assets at fair value through profit and loss	3	(8)
Other interest income	38	20
Finance income	234	115
Interest costs [abstract]
Interest expense on financial instruments	(950)	(903)
Unwinding of discount on provisions and other liabilities	(64)	(50)
Other interest	(21)	(8)
Net (losses) gains on derivative financial instruments	(15)	34
Less: interest capitalised	134	127
Finance costs	(916)	(800)
Net finance costs	(682)	(685)
Principal accretion on inflation-linked debt	87	149
Principal accretion on inflation-linked swaps, expense (income)	£ (4)	£ 18
Capitalisation rate of borrowing costs eligible for capitalisation	4.30%	4.70%
Tax relief on capitalised interest	£ 16	£ 21

Assets held for sale and disc_3

Assets held for sale and discontinued operations - Schedule of assets and liabilities classified as held for sale (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	£ 3,731	£ 1,823
Total liabilities held for sale	(1,309)	(1,474)
Assets and liabilities classified as held for sale
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	3,731	1,823
Total liabilities held for sale	(1,309)	(1,474)
Net assets (liabilities) classified as held for sale	2,422	349
Assets and liabilities classified as held for sale \| National Grid Renewables
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	1,146	0
Total liabilities held for sale	(10)	0
Net assets (liabilities) classified as held for sale	1,136	0
Assets and liabilities classified as held for sale \| Grain LNG
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	1,036	0
Total liabilities held for sale	(307)	0
Net assets (liabilities) classified as held for sale	729	0
Assets and liabilities classified as held for sale \| UK Electricity System Operator
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	1,549	1,134
Total liabilities held for sale	(992)	(1,427)
Net assets (liabilities) classified as held for sale	557	(293)
Assets and liabilities classified as held for sale \| RAA
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	0	0
Total liabilities held for sale	0	(47)
Net assets (liabilities) classified as held for sale	0	(47)
Assets and liabilities classified as held for sale \| GasT TopCo Limited
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Total assets held for sale	0	689
Total liabilities held for sale	0	0
Net assets (liabilities) classified as held for sale	£ 0	£ 689

Assets held for sale and disc_4

Assets held for sale and discontinued operations - Narrative (Details) - GBP (£) £ in Millions					6 Months Ended
	Oct. 01, 2024	Sep. 26, 2024	Mar. 11, 2024	Jan. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Profit (loss)					£ 648	£ 1,129
UK Electricity System Operator
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Profit (loss)					103	455
UK Electricity System Operator \| Other disposals of assets
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Consideration paid (received)	£ 630
NGR and Grain LNG
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Profit (loss)					£ 52	£ 83
GasT TopCo Limited
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Consideration paid (received)		£ 686
Proportion of ownership interest disposed			20%
Proportion of ownership interest in associate			20%	40%
Gains (losses) on disposals of assets		£ 25
GasT TopCo Limited \| Consortium
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Proportion of ownership interest in associate				60%
UK Gas Transmission
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Proportion of ownership interest disposed				100%
Portion of consideration received				£ 4,000
Portion of consideration received consisting of shareholding in acquirer				40%

Assets held for sale and disc_5

Assets held for sale and discontinued operations - Schedule of assets and liabilities classified as held for sale, ESO (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Intangible assets	£ 3,393	£ 3,431
Property, plant and equipment	69,195	68,907
Pension asset	2,478	2,407
Cash and cash equivalents	1,125	559
Financial investments	558	368
Total assets	101,852	98,325
Borrowings	(45,176)	(47,072)
Total liabilities	(65,986)	(68,433)
Net assets	35,866	£ 29,892
Assets and liabilities classified as held for sale \| UK Electricity System Operator
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Intangible assets	485
Property, plant and equipment	121
Trade and other receivables	375
Pension asset	16
Cash and cash equivalents	51
Financial investments	501
Total assets	1,549
Borrowings	(13)
Other liabilities	(632)
Provision for UK electricity balancing costs	(347)
Total liabilities	(992)
Net assets	£ 557

Assets held for sale and disc_6

Assets held for sale and discontinued operations - Schedule of assets and liabilities classified as held for sale, NGR Grain LNG (Details) (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Goodwill	£ 9,367	£ 9,729
Other intangible assets	3,393	3,431
Property, plant and equipment	69,195	68,907
Cash and cash equivalents	1,125	559
Financial investments	6,942	4,332
Total assets	101,852	98,325
Borrowings	(45,176)	(47,072)
Total liabilities	(65,986)	(68,433)
Net assets	35,866	£ 29,892
Assets and liabilities classified as held for sale \| National Grid Renewables
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Goodwill	80
Other intangible assets	0
Property, plant and equipment	90
Investments in joint ventures and associates	704
Trade and other receivables	74
Cash and cash equivalents	39
Financial investments	23
Other assets	136
Total assets	1,146
Borrowings	(2)
Other liabilities	(8)
Total liabilities	(10)
Net assets	1,136
Assets and liabilities classified as held for sale \| Grain LNG
Disclosure Of Detailed Information About Assets Held For Sale [Line Items]
Goodwill	0
Other intangible assets	5
Property, plant and equipment	856
Investments in joint ventures and associates	0
Trade and other receivables	47
Cash and cash equivalents	106
Financial investments	0
Other assets	22
Total assets	1,036
Borrowings	(120)
Other liabilities	(187)
Total liabilities	(307)
Net assets	£ 729

Assets held for sale and disc_7

Assets held for sale and discontinued operations - Summary of discontinued operations in the Income Statement (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of analysis of single amount of discontinued operations [line items]
Operating profit	£ 1,309	£ 1,985
Finance income	234	115
Finance costs	(916)	(800)
Profit before tax	684	1,371
Total profit after tax from discontinued operations	76	65
Discontinued operations
Disclosure of analysis of single amount of discontinued operations [line items]
Operating profit	0	0
Finance income	5	9
Finance costs	47	61
Profit before tax	52	70
Tax	(1)	(5)
Profit after tax from discontinued operations	51	65
Gain on disposal	25	0
Total profit after tax from discontinued operations	£ 76	£ 65

Assets held for sale and disc_8

Assets held for sale and discontinued operations - Summary of discontinued operations in the Statement of Comprehensive Income (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Disclosure of analysis of single amount of discontinued operations [line items]
Profit after tax from discontinued operations	£ 76	£ 65
Items from discontinued operations that may be reclassified subsequently to profit or loss:
Net gains/(losses) on investments in debt instruments measured at fair value through other comprehensive income	13	(16)
Tax on items that may be reclassified subsequently to profit or loss	(17)	(59)
Total items from continuing operations that may be reclassified subsequently to profit or loss	(737)	284
Other comprehensive loss for the period, net of tax, from discontinued operations	(729)	74
Total comprehensive (loss)/income for the period	(81)	1,203
Discontinued operations
Disclosure of analysis of single amount of discontinued operations [line items]
Profit after tax from discontinued operations	76	65
Items from discontinued operations that may be reclassified subsequently to profit or loss:
Net gains/(losses) on investments in debt instruments measured at fair value through other comprehensive income	(13)	(12)
Tax on items that may be reclassified subsequently to profit or loss	3	3
Total items from continuing operations that may be reclassified subsequently to profit or loss	(10)	(9)
Other comprehensive loss for the period, net of tax, from discontinued operations	(10)	(9)
Total comprehensive (loss)/income for the period	£ 66	£ 56

Tax from continuing operations

Tax from continuing operations (Details) - GBP (£) £ in Millions	6 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024
Income taxes paid (refund) [abstract]
Tax expense (income), continuing operations	£ 112	£ 307
Average effective tax rate	16.40%	22.40%	27.30%

Earnings per share (Details)

Earnings per share (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Basic earnings per share [abstract]
Profit after tax from continuing operations attributable to the parent	£ 571	£ 1,063
Profit after tax from discontinued operations attributable to the parent	76	65
Total profit after tax attributable to the parent	£ 647	£ 1,128
Basic earnings per share (continuing) (in GBP per share)	£ 0.126	£ 0.267	[1]
Basic earnings per share (discontinued) (in GBP per share)	0.017	0.016
Basic earnings per share (continuing and discontinued) (in GBP per share)	£ 0.143	£ 0.283	[1]
Weighted average number of shares - basic (in shares)	4,526	3,981
Diluted earnings per share [abstract]
Profit after tax from continuing operations attributable to the parent	£ 571	£ 1,063
Profit after tax from discontinued operations attributable to the parent	76	65
Total profit after tax attributable to the parent	£ 647	£ 1,128
Diluted earnings per share (continuing) (in GBP per share)	£ 0.126	£ 0.266	[1]
Diluted earnings per share (discontinued) (in GBP per share)	0.016	0.016
Diluted earnings per share (continuing and discontinued) (in GBP per share)	£ 0.142	£ 0.282	[1]
Weighted average number of shares - diluted (in shares)	4,547	3,999

[1] Restated to reflect the impact of the bonus element of the Rights Issue (see note 9).

Rights Issue - Narrative (Detai

Rights Issue - Narrative (Details) £ / shares in Units, £ in Millions	1 Months Ended	6 Months Ended
	Jun. 30, 2024 GBP (£) £ / shares shares	Sep. 30, 2024 GBP (£)	Sep. 30, 2023 GBP (£)
Issued capital [abstract]
Net proceeds from issue or ordinary shares \| £	£ 6,839
Transaction fees related to Rights Issue \| £	£ 162	£ 162	£ 0
Increase (decrease) in number of rights issued (in shares)	1,085,000,000
Issue price (in GBP per share) \| £ / shares	£ 6.45
Shares issued, number of ordinary shares, basis (in shares)	7
Shares issued, number of ordinary shares, existing shares (in shares)	24
Discount of issue price, percent	33%
Bonus factor	1.0811

Rights Issue - Schedule of shar

Rights Issue - Schedule of share capital (Details) - GBP (£) £ / shares in Units, £ in Millions, shares in Millions	1 Months Ended	6 Months Ended
	Jun. 30, 2024	Sep. 30, 2024	Mar. 31, 2024
Disclosure of classes of share capital [line items]
Par value per share (in GBP per share)		£ 0.1243129
Issued in Rights Issue (in shares)	1,085
Equity, beginning balance		£ 29,892
Issued in Rights Issue		6,839
Equity, ending balance		£ 35,866
Number of shares held by the Company (in shares)		241	247
Share capital
Disclosure of classes of share capital [line items]
Issued capital, beginning balance (in shares)		3,967
Issued in Rights Issue (in shares)		1,085
Issued during the period in lieu of dividends (in shares)		74
Issued capital, ending balance (in shares)		5,126
Equity, beginning balance		£ 493
Issued in Rights Issue		135
Issued during the period in lieu of dividends		9
Equity, ending balance		£ 637

Dividends - Schedule of dividen

Dividends - Schedule of dividends (Details) - GBP (£) £ / shares in Units, £ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Final dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)	£ 0.3912	£ 0.3760
Cash dividend paid	£ 811	£ 1,325
Scrip dividend	£ 643	£ 56
Interim dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)	£ 0.1940
Cash dividend paid	£ 393
Scrip dividend	£ 320

Dividends - Schedule of divid_2

Dividends - Schedule of dividends per share adjusted (Details)	1 Months Ended	12 Months Ended
	Jun. 30, 2024	Mar. 31, 2024 £ / shares	Mar. 31, 2023 £ / shares
Summary Of Dividends [Line Items]
Bonus factor	1.0811
Final dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)		£ 0.3912	£ 0.3760
Impact of rights issue (in GBP per share)		(0.0293)	(0.0282)
Adjusted dividend (in GBP per share)		0.3619	£ 0.3478
Interim dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)		0.1940
Impact of rights issue (in GBP per share)		(0.0146)
Adjusted dividend (in GBP per share)		£ 0.1794

Dividends - Narrative (Details)

Dividends - Narrative (Details) - GBP (£) £ / shares in Units, £ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Summary Of Dividends [Line Items]
Dividends declared before financial statements authorised for issue (GBP per share)	£ 0.1584
Dividends declared before financial statements authorised for issue	£ 774
Final dividend
Summary Of Dividends [Line Items]
Cash dividend paid (in GBP per share)		£ 0.3912	£ 0.3760
Cash dividend paid		£ 811	£ 1,325
Scrip dividend		£ 643	£ 56

Fair value measurement - Schedu

Fair value measurement - Schedule of assets and liabilities measured at fair value (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	£ 6,942	£ 4,332
Financial liabilities	(1,273)	(1,244)
Total	5,669	3,088
Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	5,589	3,084
Financial liabilities	0	0
Total	5,589	3,084
Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	890	725
Financial liabilities	(1,146)	(1,127)
Total	(256)	(402)
Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	463	523
Financial liabilities	(127)	(117)
Total	336	406	£ 355	£ 297
Financing derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(1,149)	(1,126)
Financing derivatives \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Financing derivatives \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(1,044)	(1,022)
Financing derivatives \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(105)	(104)
Commodity contract derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(124)	(118)
Commodity contract derivatives \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	0	0
Commodity contract derivatives \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(102)	(105)
Commodity contract derivatives \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial liabilities	(22)	(13)
Investments held at fair value through profit and loss
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	5,995	3,567
Investments held at fair value through profit and loss \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	5,589	3,084
Investments held at fair value through profit and loss \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	0	0
Investments held at fair value through profit and loss \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	406	483
Investments held at fair value through other comprehensive income
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	389	397
Investments held at fair value through other comprehensive income \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	0	0
Investments held at fair value through other comprehensive income \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	389	397
Investments held at fair value through other comprehensive income \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	0	0
Financing derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	520	333
Financing derivatives \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	0	0
Financing derivatives \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	467	293
Financing derivatives \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	53	40
Commodity contract derivatives
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	38	35
Commodity contract derivatives \| Level 1
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	0	0
Commodity contract derivatives \| Level 2
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	34	35
Commodity contract derivatives \| Level 3
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Financial investments	£ 4	£ 0

Fair value measurement - Narrat

Fair value measurement - Narrative (Details) £ in Millions	Sep. 30, 2024 GBP (£) investment	Mar. 31, 2024 GBP (£)
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings \| £	£ 45,176	£ 47,072
Number of equity investments	38
Number of equity investments valued based on latest transaction price	11
Number of equity investments valued based on internal valuation process	25
At fair value
Disclosure Of Fair Value Measurement Of Assets And Liabilities [Line Items]
Borrowings \| £	£ 41,604	£ 42,617

Fair value measurement - Sche_2

Fair value measurement - Schedule of impacts of reasonably possible changes in significant Level 3 assumptions (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Sep. 30, 2023
Financing derivatives \| +20 basis point increase in Limited Price Index (LPI) market curve
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+20 basis point increase in Limited Price Index (LPI) market curve	£ (40)	£ (38)
Financing derivatives \| -20 basis point decrease in LPI market curve
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-20 basis point decrease in LPI market curve	38	38
Financing derivatives \| +20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI)
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI)	36	36
Financing derivatives \| -20 basis point decrease between RPI and CPI market curves
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-20 basis point decrease between RPI and CPI market curves	(33)	(33)
Commodity contract derivatives \| 10% increase in commodity prices
Disclosure of sensitivity analysis for actuarial assumptions [line items]
10% increase in commodity prices	2	15
Commodity contract derivatives \| 10% decrease in commodity prices
Disclosure of sensitivity analysis for actuarial assumptions [line items]
10% decrease in commodity prices	(2)	(15)
Commodity contract derivatives \| +10% market area price change
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+10% market area price change	11	12
Commodity contract derivatives \| -10% market area price change
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-10% market area price change	(10)	(11)
Other \| +100 basis points change in discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+100 basis points change in discount rate	(6)	(8)
Other \| -100 basis points change in discount rate
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-100 basis points change in discount rate	7	9
Other \| +10% change in venture capital price
Disclosure of sensitivity analysis for actuarial assumptions [line items]
+10% change in venture capital price	26	30
Other \| -10% change in venture capital price
Disclosure of sensitivity analysis for actuarial assumptions [line items]
-10% change in venture capital price	£ (26)	£ (30)

Fair value measurement - Sche_3

Fair value measurement - Schedule of reconciliation of changes in Level 3 (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	£ 3,088
Financial assets (liabilities), ending balance	5,669
Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	406	£ 297
Net gains/(losses) through the consolidated income statement for the period	(61)	47
Purchases	19	1
Settlements	(38)	10
Reclassification/transfer out of level 3	10	0
Financial assets (liabilities), ending balance	336	355
Financing derivatives \| Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(64)	(100)
Net gains/(losses) through the consolidated income statement for the period	12	25
Purchases	0	0
Settlements	0	0
Reclassification/transfer out of level 3	0	0
Financial assets (liabilities), ending balance	(52)	(75)
Gains (losses) recognized in P&L	12	25
Commodity contract derivatives \| Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	(13)	(36)
Net gains/(losses) through the consolidated income statement for the period	(19)	(4)
Purchases	0	(10)
Settlements	4	7
Reclassification/transfer out of level 3	10	0
Financial assets (liabilities), ending balance	(18)	(43)
Gains (losses) recognized in P&L	19	4
Other \| Level 3
Changes In Fair Value Measurement, Assets (Liabilities) [Roll Forward]
Financial assets (liabilities), beginning balance	483	433
Net gains/(losses) through the consolidated income statement for the period	(54)	26
Purchases	19	11
Settlements	(42)	3
Reclassification/transfer out of level 3	0	0
Financial assets (liabilities), ending balance	£ 406	£ 473

Net debt - Schedule of componen

Net debt - Schedule of components of net debt (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure of detailed information about financial instruments [line items]
Cash and cash equivalents	£ 1,125	£ 559
Current financial investments	6,140	3,699
Borrowings	(45,176)	(47,072)
Financing derivatives	(629)	(793)
Net debt (net of related derivative financial instruments)	(38,540)	(43,607)
Derivative liabilities	715	876
Derivatives \| Capital expenditure prepayments
Disclosure of detailed information about financial instruments [line items]
Derivative liabilities	£ 58	£ 36

Net debt - Schedule of balance

Net debt - Schedule of balance sheet allocation of derivative balances (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Disclosure of detailed information about financial instruments [line items]
Financial investments	£ 558	£ 368
Derivative financial liabilities	(1,273)	(1,244)
Financing derivatives	(715)	(876)
Financing derivatives
Disclosure of detailed information about financial instruments [line items]
Financial investments	520	333
Derivative financial liabilities	(1,149)	(1,126)
Financing derivatives	(629)	(793)
Commodity contract derivatives
Disclosure of detailed information about financial instruments [line items]
Financial investments	38	35
Derivative financial liabilities	(124)	(118)
Financing derivatives	£ (86)	£ (83)

Pensions and other post-retir_3

Pensions and other post-retirement benefit obligations - Schedule of defined benefit plan recognised in balance sheet (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Mar. 31, 2023
Disclosure of defined benefit plans [line items]
Other post-employment liabilities	£ (61)	£ (52)
Net defined benefit asset	1,875	1,814	£ 1,737	£ 1,951
Net defined benefit asset	2,478	2,407
Liabilities	(603)	(593)
Funded obligations
Disclosure of defined benefit plans [line items]
Present value of obligations	(17,058)	(17,601)
Fair value of plan assets	19,247	19,733
Funding surplus/(deficit)	2,189	2,132
Unfunded obligations
Disclosure of defined benefit plans [line items]
Present value of obligations	£ (253)	£ (266)

Pensions and other post-retir_4

Pensions and other post-retirement benefit obligations - Schedule of key actuarial assumptions (Details)	Sep. 30, 2024	Mar. 31, 2024
UK
Disclosure of defined benefit plans [line items]
Discount rate – UK past service	5.02%	4.87%
Rate of increase in RPI – UK past service	2.95%	3.05%
US
Disclosure of defined benefit plans [line items]
Discount rate – US	4.90%	5.15%

Pensions and other post-retir_5

Pensions and other post-retirement benefits - Schedule of reconciliation of the net defined benefit asset (Details) - GBP (£) £ in Millions	6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Employee Benefits [Abstract]
Opening net defined benefit asset	£ 1,814	£ 1,951
Changes in net defined benefit liability (asset) [abstract]
Cost recognised in the income statement	(29)	(34)
Employer contributions	81	80
Remeasurement and foreign exchange effects recognised in the statement of other comprehensive income	18	(257)
Other movements	(9)	(3)
Closing net defined benefit asset	£ 1,875	£ 1,737

Pensions and other post-retir_6

Pensions and other post-retirement benefit obligations - Narrative (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
UK
Disclosure of defined benefit plans [line items]
Funding surplus/(deficit)	£ 1,359	£ 1,317
US
Disclosure of defined benefit plans [line items]
Funding surplus/(deficit)	£ 1,119	£ 1,090

Commitments and contingencies (

Commitments and contingencies (Details) - GBP (£) £ in Millions	Sep. 30, 2024	Mar. 31, 2024
Subclassifications of assets, liabilities and equities [abstract]
Energy purchase commitments	£ 13,403	£ 14,175
Contractual capital commitments	£ 3,697	£ 3,250

Exchange rates (Details)

Exchange rates (Details) - $ / £	6 Months Ended		12 Months Ended
Exchange rates (Details) - $ / £	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024
Foreign exchange rates [abstract]
Closing rate applied at period end	1.34	1.22	1.26
Average rate applied for the period	1.30	1.25	1.26

Post balance sheet events (Deta

Post balance sheet events (Details) £ in Billions	Oct. 31, 2024 GBP (£)
Entering into significant commitments \| Pensions
Disclosure of non-adjusting events after reporting period [line items]
Defined benefit plan, buy-in-transaction	£ 1.7