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 £ 889 £ 1,184
Favorable changes, Equity 47 47
Unfavorable changes, Income Statement (970) (1,507)
Unfavorable changes, Equity (47) (47)
Interest rate risk    
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 risk    
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 261 577
Favorable changes, Equity 38 43
Unfavorable changes, Income Statement (260) (742)
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 27 28
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (27) (28)
Unfavorable changes, Equity 0 0
Other Products    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 81 91
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (96) (104)
Unfavorable changes, Equity £ 0 £ 0