v3.25.4
Property, Plant and Equipment and Investment Property - Additional Information (Detail) - GBP (£)
£ in Millions
 12 Months Ended
Jan. 01, 2025
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of detailed information about property, plant and equipment [line items]        
Disposals, property, plant and equipment   £ 3 £ 4  
Reversal of Impairment   20 (1)  
Additions to right of use assets   51 46  
Rental income from investment property   10 9 £ 6
Classification of assets as held for sale [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Reversal of Impairment   3    
Property, plant and equipment [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Disposals, property, plant and equipment £ 3      
Property, plant and equipment, gross carrying amount of fully depreciated assets still in use £ 0      
Right-of-use assets [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Reversal of Impairment   17    
Investment property [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Additions to right of use assets   10 7  
Cost of goods sold [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Depreciation expense   39 42 40
Operating expense [member]        
Disclosure of detailed information about property, plant and equipment [line items]        
Depreciation expense   35 34 39
Reversal of Impairment   £ 20 £ (1) £ (2)