v3.25.4
Classification of Financial Instruments - Schedule of Accounting Classification of Class of Financial Liabilities, Together with their Carrying Values and Market Values (Detail) - GBP (£)
£ in Millions
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of financial liabilities [line items]      
Financial liabilities £ (1,782) £ (1,825)  
Total market value (1,761) (1,788)  
Derivative financial instruments [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (3) (58)  
Total market value (3) (58)  
Trade payables [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (281) (273)  
Total market value (281) (273)  
Deferred And Contingent Consideration [Member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (17) (22)  
Total market value (17) (22) £ (57)
Borrowings [member] | In less than one year [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (62) (315)  
Total market value (62) (312)  
Borrowings [member] | More than 12 months past due date [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (1,419) (1,157)  
Total market value (1,398) (1,123)  
FVTPL [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (3) (11)  
FVTPL [member] | Derivative financial instruments [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (2) (10)  
FVTPL [member] | Trade payables [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
FVTPL [member] | Deferred And Contingent Consideration [Member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (1) (1)  
FVTPL [member] | Borrowings [member] | Financial liabilities at fair value [member] | In less than one year [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
FVTPL [member] | Borrowings [member] | Financial liabilities at fair value [member] | More than 12 months past due date [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Financial liabilities derivatives in hedging relationship [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (1) (48)  
Financial liabilities derivatives in hedging relationship [member] | Derivative financial instruments [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (1) (48)  
Financial liabilities derivatives in hedging relationship [member] | Trade payables [member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Financial liabilities derivatives in hedging relationship [member] | Deferred And Contingent Consideration [Member] | Financial liabilities at fair value [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Financial liabilities derivatives in hedging relationship [member] | Borrowings [member] | Financial liabilities at fair value [member] | In less than one year [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Financial liabilities derivatives in hedging relationship [member] | Borrowings [member] | Financial liabilities at fair value [member] | More than 12 months past due date [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Other Financial Liability [member] | Financial liabilities at amortised cost [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (1,778) (1,766)  
Other Financial Liability [member] | Derivative financial instruments [member] | Financial liabilities at amortised cost [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities 0 0  
Other Financial Liability [member] | Trade payables [member] | Financial liabilities at amortised cost [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (281) (273)  
Other Financial Liability [member] | Deferred And Contingent Consideration [Member] | Financial liabilities at amortised cost [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (16) (21)  
Other Financial Liability [member] | Borrowings [member] | Financial liabilities at amortised cost [member] | In less than one year [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities (62) (315)  
Other Financial Liability [member] | Borrowings [member] | Financial liabilities at amortised cost [member] | More than 12 months past due date [member]      
Disclosure of financial liabilities [line items]      
Financial liabilities £ (1,419) £ (1,157)