v3.25.4
Financial instruments - Market risk - Additional information (Details) - Market risk - GBP (£)
£ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of detailed information about financial instruments    
Percentage of borrowings at fixed rates 66.00%  
Reasonably possible reduction in short-term interest rates 1.00%  
Decrease in net finance costs due to reasonably possible reduction in short-term interest rates £ 23 £ 28
Reasonably possible increase in short-term interest rates 1.00%  
Increase in net finance costs due to reasonably possible increase in short-term interest rates £ 23 28
Decrease in equity due to reasonably possible decrease in short-term interest rate. 4 0
Increase in equity due to reasonably possible increase in short-term interest rate. £ 4 0
Highly predictable future cash flows hedging period 24 months  
Assumed weakening of foreign currencies 10.00%  
Decrease in carrying value of net assets, excluding net borrowings, due to assumed weakening of foreign currencies £ 792 852
Decrease in net borrowings, due to assumed weakening of foreign currencies £ 654 683
Assumed strengthening of foreign currencies 10.00%  
Increase in carrying value of net assets, excluding net borrowings, due to assumed strengthening of foreign currencies £ 792 852
Increase in net borrowings, due to assumed strengthening of foreign currencies 654 683
Decrease in net profit, due to assumed weakening of foreign currencies 170 156
Increase in net profit, due to assumed strengthening of foreign currencies £ 170 £ 156
Scientific, Technical & Medical | Subscriptions    
Disclosure of detailed information about financial instruments    
Highly predictable future cash flows hedging period 50 months