v3.25.4
Derivative financial instruments - Schedule of Hedged Items and Gains and Losses Arising from Hedge Accounting (Details) - Fair value hedges - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Carrying amount of the hedged item, assets £ 156,790 £ 153,277  
Carrying amount of the hedged item, liabilities 45,053 51,499  
Accumulated amount of fair value adjustment on the hedged item, assets (1,231) (1,960)  
Accumulated fair value hedge adjustment on hedged item included in carrying amount, liabilities 829 1,340  
Change in fair value of hedged item for ineffectiveness assessment £m 57 (1,417)  
Hedge ineffectiveness recognised in the income statement £m (54) (81) £ (267)
Interest rate      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Hedge ineffectiveness recognised in the income statement £m (54) (81)  
Fixed rate mortgages      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Carrying amount of the hedged item, assets 121,732 124,013  
Carrying amount of the hedged item, liabilities 0 0  
Accumulated amount of fair value adjustment on the hedged item, assets (178) (890)  
Accumulated fair value hedge adjustment on hedged item included in carrying amount, liabilities 0 0  
Change in fair value of hedged item for ineffectiveness assessment £m 725 (184)  
Fixed rate mortgages | Interest rate      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Hedge ineffectiveness recognised in the income statement £m (68) (52)  
Fixed rate issuance      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Carrying amount of the hedged item, assets 0 0  
Carrying amount of the hedged item, liabilities 45,053 51,499  
Accumulated amount of fair value adjustment on the hedged item, assets 0 0  
Accumulated fair value hedge adjustment on hedged item included in carrying amount, liabilities 829 1,340  
Change in fair value of hedged item for ineffectiveness assessment £m (530) (75)  
Fixed rate issuance | Interest rate      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Hedge ineffectiveness recognised in the income statement £m 10 (11)  
Fixed rate bonds      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Carrying amount of the hedged item, assets 35,058 29,264  
Carrying amount of the hedged item, liabilities 0 0  
Accumulated amount of fair value adjustment on the hedged item, assets (1,053) (1,070)  
Accumulated fair value hedge adjustment on hedged item included in carrying amount, liabilities 0 0  
Change in fair value of hedged item for ineffectiveness assessment £m (138) (1,158)  
Fixed rate bonds | Interest rate      
DERIVATIVE FINANCIAL INSTRUMENTS (Details) - Schedule of the effects of hedge accounting [Line Items]      
Hedge ineffectiveness recognised in the income statement £m £ 4 £ (18)