v3.26.1
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, 2026
Dec. 31, 2025
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement £ 1,028 £ 972
Favorable changes, Equity 25 339
Unfavorable changes, Income Statement (1,066) (1,060)
Unfavorable changes, Equity (75) (132)
Interest rate derivatives    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 127 109
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (132) (134)
Unfavorable changes, Equity 0 0
Equity derivatives    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 375 336
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (375) (336)
Unfavorable changes, Equity 0 0
Loans    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 187 201
Favorable changes, Equity 3 21
Unfavorable changes, Income Statement (229) (297)
Unfavorable changes, Equity (40) (37)
Corporate debt    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 72 88
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (87) (68)
Unfavorable changes, Equity 0 0
Asset backed securities    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 110 51
Favorable changes, Equity 1 6
Unfavorable changes, Income Statement (88) (43)
Unfavorable changes, Equity (1) (6)
Government and Government sponsored debt    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 55 45
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (53) (41)
Unfavorable changes, Equity 0 0
Private equity investments    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 47 37
Favorable changes, Equity 0 0
Unfavorable changes, Income Statement (47) (37)
Unfavorable changes, Equity 0 0
Other products    
Disclosure of detailed information about financial instruments [line items]    
Favorable changes, Income Statement 55 105
Favorable changes, Equity 21 312
Unfavorable changes, Income Statement (55) (104)
Unfavorable changes, Equity £ (34) £ (89)