v3.25.4
Risk Management - Disclosure of analysis of equity sensitivity (Details) - Interest rate risk - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
+/- 25bps    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in profit for the year due to reasonable possibly increase £ (25) £ (9)
Increase (decrease) in profit for the year due to reasonably possible decrease £ 23 £ 8
Increase (decrease) in profit for the year due to reasonable possibly increase, percentage (0.50%) (0.20%)
Increase (decrease) in profit for the year due to reasonable possibly decrease, percentage 0.50% 0.20%
Increase (decrease) in equity for the year due to reasonable possible increase £ (751) £ (571)
Increase (decrease) in equity for the year due to reasonable possible decrease £ 755 £ 575
Increase (decrease) in equity for the year due to reasonable possible increase, percentage (1.20%) (1.00%)
Increase (decrease) in equity for the year due to reasonable possible decrease, percentage 1.20% 1.00%
Net interest income    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in profit for the year due to reasonable possibly increase £ (33) £ (11)
Increase (decrease) in profit for the year due to reasonably possible decrease 31 10
Effect on profit for the year (per above)    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in equity for the year due to reasonable possible increase (25) (9)
Increase (decrease) in equity for the year due to reasonable possible decrease 23 8
Fair value through other comprehensive income reserve    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in equity for the year due to reasonable possible increase (186) (193)
Increase (decrease) in equity for the year due to reasonable possible decrease 193 200
Cash flow hedge reserve    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in equity for the year due to reasonable possible increase (823) (588)
Increase (decrease) in equity for the year due to reasonable possible decrease 823 588
Taxation effects on the above    
Disclosure of sensitivity analysis to changes in risk exposures that arise from contracts within scope of IFRS 17 [line items]    
Increase (decrease) in profit for the year due to reasonable possibly increase 8 2
Increase (decrease) in profit for the year due to reasonably possible decrease (8) (2)
Increase (decrease) in equity for the year due to reasonable possible increase 283 219
Increase (decrease) in equity for the year due to reasonable possible decrease £ (284) £ (221)