v3.26.1
Other equity reserves (Details) - GBP (£)
£ in Millions
 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance £ (4,233) £ (3,990) £ (3,860)
Exchange adjustments (348) (352) (335)
Exchange differences reclassified to the consolidated income statement on disposal 76 0 0
Net gains/(losses) taken to equity 415 (28) 87
Transferred to profit or loss (493) 182 213
Rights Issue   6,704  
Transfer to retained earnings   (6,704)  
Net gains (losses) in respect of cash flow hedging of capital expenditure 22 (16) (37)
Tax 16 (34) (60)
Cash flow hedges transferred to the statement of financial position, net of tax 3 5 2
Other equity reserves, ending balance (4,542) (4,233) (3,990)
Gains (losses) on exchange differences on translation of foreign operations (380) (408) (397)
Net gains (losses) in respect of net investment hedges 32 56 62
National Grid Renewables      
Disclosure of reserves within equity [line items]      
Exchange differences reclassified to the consolidated income statement on disposal 84    
Net gains (losses) in respect of net investment hedges 8    
Translation      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance 619 971 1,306
Exchange adjustments (348) (352) (335)
Exchange differences reclassified to the consolidated income statement on disposal 76    
Other equity reserves, ending balance 347 619 971
Cash flow hedge      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance 251 94 (61)
Net gains/(losses) taken to equity 368 30 16
Transferred to profit or loss (489) 188 224
Net gains (losses) in respect of cash flow hedging of capital expenditure 22 (16) (37)
Tax 25 (50) (50)
Cash flow hedges transferred to the statement of financial position, net of tax 3 5 2
Other equity reserves, ending balance 180 251 94
Cost of hedging      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance (57) (18) (38)
Net gains/(losses) taken to equity 40 (46) 37
Transferred to profit or loss (4) (6) (11)
Tax (9) 13 (6)
Other equity reserves, ending balance (30) (57) (18)
FVOCI debt      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance 100 109 79
Net gains/(losses) taken to equity 7 (12) 34
Tax   3 (4)
Other equity reserves, ending balance 107 100 109
Capital redemption      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance 19 19 19
Other equity reserves, ending balance 19 19 19
Merger      
Disclosure of reserves within equity [line items]      
Other equity reserves, beginning balance (5,165) (5,165) (5,165)
Rights Issue   6,704  
Transfer to retained earnings   (6,704)  
Other equity reserves, ending balance £ (5,165) £ (5,165) £ (5,165)