v3.26.1
Share-based Payments - Additional Information (Detail)
£ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
GBP (£)
Jun. 30, 2025
GBP (£)
Jun. 30, 2026
GBP (£)
yr
shares
Plan
Jun. 30, 2025
GBP (£)
shares
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Share-based payment expense | £ £ 0.9 £ 8.0 £ 2.8 £ 8.2
Number of equity settled share-based payment plans | Plan     6  
Maximum [member] | Employees [member]        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Expected option life (years)     10  
Maximum [member] | Directors [member]        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Expected option life (years)     10  
Maximum [member] | Consultants [member]        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Expected option life (years)     10  
Long-Term Incentive Plan [member]        
Disclosure of terms and conditions of share-based payment arrangement [line items]        
Number of share options granted in share-based payment arrangement | shares     4,121,000,000 3,478,000,000