v3.26.1
Derivative financial instruments - Schedule of maturity profile of financing derivatives (Details) - GBP (£)
£ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of detailed information about financial instruments [line items]    
Derivative assets £ 838 £ 482
Derivative liabilities (1,018) (1,202)
Total (180) (720)
More than 5 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 0 0
Derivative liabilities 0 (2)
Total 0 (2)
Financing derivatives    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 717 375
Derivative liabilities (950) (1,138)
Total (233) (763)
Financing derivatives | Less than 1 year    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 123 19
Derivative liabilities (237) (355)
Total (114) (336)
Financing derivatives | Over 12 months past due    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 594 356
Derivative liabilities (713) (783)
Total (119) (427)
Financing derivatives | In 1 to 2 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 88 46
Derivative liabilities (86) (61)
Total 2 (15)
Financing derivatives | In 2 to 3 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 69 41
Derivative liabilities (45) (77)
Total 24 (36)
Financing derivatives | In 3 to 4 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 34 47
Derivative liabilities (17) (73)
Total 17 (26)
Financing derivatives | In 4 to 5 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 51 6
Derivative liabilities (8) (25)
Total 43 (19)
Financing derivatives | More than 5 years    
Disclosure of detailed information about financial instruments [line items]    
Derivative assets 352 216
Derivative liabilities (557) (547)
Total £ (205) £ (331)