v3.26.1
Basis of preparation (Details)
£ in Millions
6 Months Ended 12 Months Ended
Jun. 30, 2026
GBP (£)
uSD / gBP
Jun. 30, 2026
GBP (£)
€ / gBP
Dec. 31, 2025
GBP (£)
uSD / gBP
Dec. 31, 2025
GBP (£)
€ / gBP
Jun. 30, 2026
uSD / gBP
Jun. 30, 2026
€ / gBP
Dec. 31, 2025
uSD / gBP
Dec. 31, 2025
€ / gBP
Disclosure of basis of preparation [Line Items]                
Cash and cash equivalents £ 2,363 £ 2,363 £ 2,694 £ 2,694        
Average exchange rate 1.35 1.15 1.30 1.19        
Closing exchange rate         1.33 1.16 1.37 1.17
Increase (decrease) due to changes in accounting policy required by IFRSs                
Disclosure of basis of preparation [Line Items]                
Cash and cash equivalents     £ 180 £ 180        
Trade and other payables     £ 180 £ 180