v3.25.3
Fair value measurement (Tables)
 6 Months Ended
Sep. 30, 2025
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 237 of the Annual Report and Accounts for the year ended 31 March 2025.
30 September 202531 March 2025
Level 1
£m		Level 2
£m		Level 3
£m		Total
£m		Level 1
£m		Level 2
£m		Level 3
£m		Total
£m
Assets
Investments held at fair value through profit and loss2,635 — 406 3,041 5,156 — 407 5,563 
Investments held at fair value through other comprehensive income1
— 382 — 382 — 384 — 384 
Financing derivatives— 822 29 851 — 344 31 375 
Commodity contract derivatives— 73 52 125 — 102 5 107 
2,635 1,277 487 4,399 5,156 830 443 6,429 
Liabilities
Financing derivatives— (755)(90)(845)— (1,043)(95)(1,138)
Commodity contract derivatives— (56)(12)(68)— (39)(25)(64)
— (811)(102)(913)— (1,082)(120)(1,202)
Total2,635 466 385 3,486 5,156 (252)323 5,227 
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 derivativesCommodity contract derivatives
Other1
Total
20252024202520242025202420252024
£m£m£m£m£m£m£m£m
At 1 April(64)(64)(20)(13)407 483 323 406 
Net gains/(losses) through the consolidated income statement for the period2,3
3 12 72 (19)(9)(54)66 (61)
Purchases— — — — 9 19 9 19 
Settlements— — (12)4 (1)(42)(13)(38)
Reclassification/transfers out of level 34
— — — 10 — — — 10 
At 30 September
(61)(52)40 (18)406 406 385 336 
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 revenue in the consolidated income statement.
2.Gains of £3 million (2024: gains of £12 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the consolidated income statement. 
3.Gains of £72 million (2024: losses of £19 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 prior 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 September202520242025202420252024
£m£m£m£m£m£m
10% increase in commodity prices— — 3 2 — — 
10% decrease in commodity prices— — (2)(2)— — 
+10% market area price change— — 1 11 — — 
-10% market area price change— — (2)(10)— — 
+20 basis point increase in Limited Price Index
(LPI) market curve		(32)(40)— — — — 
-20 basis point decrease in LPI market curve30 38 — — — — 
+20 basis point increase between Retail Price Index (RPI) and Consumer Price Index (CPI)29 36 — — — — 
-20 basis point decrease between RPI and CPI(27)(33)— — — — 
+100 basis points change in discount rate— — — — (6)(6)
-100 basis points change in discount rate— — — — 7 7 
+10% change in venture capital price— — — — 26 26 
-10% change in venture capital price— — — — (26)(26)
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 237 of the Annual Report and Accounts for the year ended 31 March 2025.
30 September 202531 March 2025
Level 1
£m		Level 2
£m		Level 3
£m		Total
£m		Level 1
£m		Level 2
£m		Level 3
£m		Total
£m
Assets
Investments held at fair value through profit and loss2,635 — 406 3,041 5,156 — 407 5,563 
Investments held at fair value through other comprehensive income1
— 382 — 382 — 384 — 384 
Financing derivatives— 822 29 851 — 344 31 375 
Commodity contract derivatives— 73 52 125 — 102 5 107 
2,635 1,277 487 4,399 5,156 830 443 6,429 
Liabilities
Financing derivatives— (755)(90)(845)— (1,043)(95)(1,138)
Commodity contract derivatives— (56)(12)(68)— (39)(25)(64)
— (811)(102)(913)— (1,082)(120)(1,202)
Total2,635 466 385 3,486 5,156 (252)323 5,227 
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 derivativesCommodity contract derivatives
Other1
Total
20252024202520242025202420252024
£m£m£m£m£m£m£m£m
At 1 April(64)(64)(20)(13)407 483 323 406 
Net gains/(losses) through the consolidated income statement for the period2,3
3 12 72 (19)(9)(54)66 (61)
Purchases— — — — 9 19 9 19 
Settlements— — (12)4 (1)(42)(13)(38)
Reclassification/transfers out of level 34
— — — 10 — — — 10 
At 30 September
(61)(52)40 (18)406 406 385 336 
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 revenue in the consolidated income statement.
2.Gains of £3 million (2024: gains of £12 million) are attributable to derivative financial instruments held at the end of the reporting period and have been recognised in finance costs in the consolidated income statement. 
3.Gains of £72 million (2024: losses of £19 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 prior period due to improved observability of the fair value of these instruments.