v3.24.1.1.u2
Derivative financial instruments - Schedule of fair values of commodity contract derivatives by type (Details) - GBP (£)
£ in Millions
Mar. 31, 2024
Mar. 31, 2023
Disclosure of detailed information about financial instruments [line items]    
Derivative assets £ 368 £ 429
Derivative liabilities (1,244) (1,293)
Total (876) (864)
Commodity contract derivatives    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 35 66
Derivative liabilities (118) (174)
Total (83) (108)
Forward purchases of gas    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 0 2
Derivative liabilities (3) (6)
Total (3) (4)
Electricity capacity    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 0 1
Derivative liabilities 0 0
Total 0 1
Electricity swaps    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 33 53
Derivative liabilities (82) (92)
Total (49) (39)
Electricity options    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 0 0
Derivative liabilities (1) (3)
Total (1) (3)
Gas swaps    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 2 9
Derivative liabilities (22) (42)
Total (20) (33)
Gas options    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 0 1
Derivative liabilities (10) (31)
Total £ (10) £ (30)