v3.25.4
Retirement Benefit and Other Post-retirement Obligations - Summary of Amounts Recognised in Balance Sheet (Detail) - GBP (£)
£ in Millions
Dec. 31, 2025
Dec. 31, 2024
Disclosure of net defined benefit (liability) asset [line items]    
Fair value of plan assets £ 2,999 £ 3,011
Present value of defined benefit obligation (2,493) (2,534)
Net pension asset/ (liability) 506 477
Other post-retirement medical benefit obligation (17) (19)
Other pension accruals (7) (8)
Net retirement benefit asset 482 450
Retirement benefit assets 518 491
Retirement benefit obligations (36) (41)
UK Group plan [member]    
Disclosure of net defined benefit (liability) asset [line items]    
Fair value of plan assets 2,994 2,927
Present value of defined benefit obligation (2,480) (2,443)
Net pension asset/ (liability) 514 484
Other funded plans [member]    
Disclosure of net defined benefit (liability) asset [line items]    
Fair value of plan assets 5 84
Present value of defined benefit obligation (1) (77)
Net pension asset/ (liability) 4 7
Other unfunded plans [member]    
Disclosure of net defined benefit (liability) asset [line items]    
Fair value of plan assets 0 0
Present value of defined benefit obligation (12) (14)
Net pension asset/ (liability) £ (12) £ (14)