v3.25.4
Deferred Income Tax - Schedule of Movement on Net Deferred Income Tax Account (Detail) - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance £ (11)    
Tax charge in other comprehensive income (3) £ 0 £ 20
Ending balance (31) (11)  
Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance (11) (11)  
Exchange differences (3) (3)  
Acquisitions and disposals of subsidiaries (1) 0  
Income statement benefit/(charge) (7) (3)  
Tax charge in other comprehensive income (9) 6  
Ending balance (31) (11) (11)
Trading losses [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance 76 101  
Exchange differences 0 (2)  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) (10) (23)  
Tax charge in other comprehensive income 0 0  
Ending balance 66 76 101
Accruals and other provisions [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance 64 59  
Exchange differences (2) 0  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) 2 (2)  
Tax charge in other comprehensive income (6) 7  
Ending balance 58 64 59
Retirement benefit obligations [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance (113) (114)  
Exchange differences 0 0  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) (6) 3  
Tax charge in other comprehensive income (3) (2)  
Ending balance (122) (113) (114)
Deferred revenue [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance 45 43  
Exchange differences (1) 0  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) (2) 2  
Tax charge in other comprehensive income 0 0  
Ending balance 42 45 43
Goodwill and intangibles [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance (123) (152)  
Exchange differences 0 0  
Acquisitions and disposals of subsidiaries (1) 0  
Income statement benefit/(charge) 35 29  
Tax charge in other comprehensive income 0 0  
Ending balance (89) (123) (152)
Interest limitations [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance 18 34  
Exchange differences 0 0  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) (18) (16)  
Tax charge in other comprehensive income 0 0  
Ending balance 0 18 34
Other [member] | Deferred income tax assets/ (liabilities) [member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]      
Beginning balance 22 18  
Exchange differences 0 (1)  
Acquisitions and disposals of subsidiaries 0 0  
Income statement benefit/(charge) (8) 4  
Tax charge in other comprehensive income 0 1  
Ending balance £ 14 £ 22 £ 18