v3.25.2
Other reserves - Narrative (Details) - GBP (£)
£ in Millions, shares in Millions
 6 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Disclosure of reserves within equity [line items]      
Other reserves £ 693   £ (468)
Repurchase of treasury shares (in shares) 270   818
Currency translation reserve      
Disclosure of reserves within equity [line items]      
Other reserves £ 2,054   £ 3,625
Increase (decrease) in equity (1,571) £ (46)  
Tax charge (credit) (3) (13)  
Fair value through other comprehensive income reserve      
Disclosure of reserves within equity [line items]      
Other reserves (1,465)   (1,873)
Increase (decrease) in equity 408 (505)  
Tax charge (credit) 157 (194)  
Gains (losses) on financial assets measured at fair value through other comprehensive income, before tax 499 (536)  
Reclassification adjustments on financial assets measured at fair value through other comprehensive income, before tax (68) 164  
Cash flow hedging reserve      
Disclosure of reserves within equity [line items]      
Other reserves (1,210)   (2,930)
Increase (decrease) in equity 1,720 777  
Tax charge (credit) 667 281  
Gains (losses) on financial assets measured at fair value through other comprehensive income, before tax 1,662 (824)  
Reclassification adjustments on financial assets measured at fair value through other comprehensive income, before tax (707) (1,831)  
Own credit reserve      
Disclosure of reserves within equity [line items]      
Other reserves (541)   (1,059)
Increase (decrease) in equity 518 (819)  
Tax charge (credit) 194 (309)  
Gains (losses) on change in value of foreign currency basis spreads, before tax 709 £ (1,131)  
Other reserves and treasury shares      
Disclosure of reserves within equity [line items]      
Other reserves 1,855   1,769
Increase (decrease) in equity 67   205
Treasury shares      
Disclosure of reserves within equity [line items]      
Increase (decrease) in equity £ 19   £ (1)