v3.24.1.1.u2
Derivative financial instruments - Schedule of fair values of financing 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)
Financing derivatives    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 333 363
Derivative liabilities (1,126) (1,119)
Total (793) (756)
Interest rate swaps    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 43 49
Derivative liabilities (110) (98)
Total (67) (49)
Cross-currency interest rate swaps    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 234 192
Derivative liabilities (844) (888)
Total (610) (696)
Foreign exchange forward contracts    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 16 100
Derivative liabilities (68) (11)
Total (52) 89
Foreign exchange forward contracts | Capital expenditure    
Disclosure of detailed information about financial instruments [line items]    
Total (36) (4)
Inflation-linked swaps    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 40 22
Derivative liabilities (104) (122)
Total £ (64) £ (100)