v3.25.4
Share Capital and Share Premium - Summary of Share Capital and Share Premium (Detail) - GBP (£)
shares in Thousands, £ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of classes of share capital [line items]      
Beginning Balance £ 4,053 £ 3,988 £ 4,415
Issue of ordinary shares – share option schemes 9 7 9
Buyback of equity 347 204 304
Ending balance £ 3,663 £ 4,053 £ 3,988
Beginning Balance 666,265 697,299  
Issue of ordinary shares – share option schemes 1,447 955  
Buyback of equity (31,897) (31,989)  
Ending Balance 635,815 666,265 697,299
Share premium [member]      
Disclosure of classes of share capital [line items]      
Beginning Balance £ 2,649 £ 2,642 £ 2,633
Issue of ordinary shares – share option schemes 9 7 9
Ending balance 2,658 2,649 2,642
Share capital [member]      
Disclosure of classes of share capital [line items]      
Beginning Balance 166 174  
Buyback of equity (8) (8)  
Ending balance £ 158 £ 166 £ 174