v3.25.4
Property, Plant and Equipment and Investment Property - Summary Of Property, Plant and Equipment and Investment Property (Detail) - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance £ 293 £ 296
Ending Balance 301 293
Cost [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 910 967
Exchange differences (38) 5
Additions 82 77
Disposals and retirements (50) (139)
Reclassifications and transfers 0 0
Ending Balance 904 910
Depreciation [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance (617) (671)
Exchange differences 27 (6)
Charge for the year (74) (76)
Disposals and retirements 44 137
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 17 (1)
Ending Balance (603) (617)
Investment property [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 77 79
Ending Balance 91 77
Investment property [member] | Cost [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 221 214
Exchange differences 0 0
Additions 11 7
Disposals and retirements 0 0
Reclassifications and transfers 0 0
Ending Balance 232 221
Investment property [member] | Depreciation [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance (144) (135)
Exchange differences 0 0
Charge for the year (8) (8)
Disposals and retirements 0 0
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 11 (1)
Ending Balance (141) (144)
Right-of-use assets [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 111 108
Ending Balance 111 111
Right-of-use assets [member] | Cost [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 350 342
Exchange differences (19) 2
Additions 41 39
Disposals and retirements (38) (33)
Reclassifications and transfers 0 0
Ending Balance 334 350
Right-of-use assets [member] | Depreciation [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance (239) (234)
Exchange differences 12 (2)
Charge for the year (34) (35)
Disposals and retirements 32 32
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 6 0
Ending Balance (223) (239)
Land and buildings [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 38 40
Ending Balance 34 38
Land and buildings [member] | Cost [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 151 165
Exchange differences (9) 1
Additions 0 0
Disposals and retirements 0 (22)
Reclassifications and transfers 7 7
Ending Balance 149 151
Land and buildings [member] | Depreciation [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance (113) (125)
Exchange differences 7 (2)
Charge for the year (9) (8)
Disposals and retirements 0 22
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 0 0
Ending Balance (115) (113)
Plant and equipment [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 58 60
Ending Balance 55 58
Plant and equipment [member] | Cost [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 179 237
Exchange differences (10) 1
Additions 4 4
Disposals and retirements (12) (84)
Reclassifications and transfers 18 21
Ending Balance 179 179
Plant and equipment [member] | Depreciation [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance (121) (177)
Exchange differences 8 (2)
Charge for the year (23) (25)
Disposals and retirements 12 83
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 0 0
Ending Balance (124) (121)
Assets in course of construction [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 9 9
Ending Balance 10 9
Assets in course of construction [member] | Cost [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 9 9
Exchange differences 0 1
Additions 26 27
Disposals and retirements 0 0
Reclassifications and transfers (25) (28)
Ending Balance 10 9
Assets in course of construction [member] | Depreciation [member] | Owned assets [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Beginning Balance 0 0
Exchange differences 0 0
Charge for the year 0 0
Disposals and retirements 0 0
Reclassifications and transfers 0 0
Reversal of impairment/(impairment) 0 0
Ending Balance £ 0 £ 0