v3.25.2
Fair value of financial instruments - Sensitivity analysis of valuations using unobservable inputs (Details) - Significant unobservable inputs (Level 3) - Recurring fair value measurement - GBP (£)
£ in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement £ 1,140 £ 1,465
Favorable changes, Equity 48 47
Unfavorable changes, Income Statement (1,201) (1,735)
Unfavorable changes, Equity (48) (47)
Interest rate derivatives    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 85 98
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (158) (212)
Unfavorable changes, Equity 0 0
Equity derivatives    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 221 199
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (261) (269)
Unfavorable changes, Equity 0 0
Loans    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 306 653
Favorable changes, Equity 38 43
Unfavorable changes, Income Statement (285) (766)
Unfavorable changes, Equity (38) (43)
Corporate loans    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 77 87
Favorable changes, Equity 1 0
Unfavorable changes, Income Statement (49) (56)
Unfavorable changes, Equity (1) 0
Asset backed securities    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 83 57
Favorable changes, Equity 8 4
Unfavorable changes, Income Statement (57) (40)
Unfavorable changes, Equity (8) (4)
Government debt    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 54 47
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (62) (56)
Unfavorable changes, Equity 0 0
Private equity investments    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 230 232
Favorable changes, Equity 1 0
Unfavorable changes, Income Statement (230) (232)
Unfavorable changes, Equity (1) 0
Other Products    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 84 92
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (99) (104)
Unfavorable changes, Equity £ 0 £ 0