Leases - Summary of maturities of operating lease payments (Detail) - GBP (£) £ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Disclosure of maturity analysis of operating lease payments [line items] | ||
| Undiscounted lease liabilities | £ 581 | £ 631 |
| Lease liabilities included in the balance sheet | 478 | 517 |
| Current | 62 | 65 |
| Non-current | 416 | 452 |
| Less than one year [Member] | ||
| Disclosure of maturity analysis of operating lease payments [line items] | ||
| Undiscounted lease liabilities | 81 | 85 |
| One to five years [member] | ||
| Disclosure of maturity analysis of operating lease payments [line items] | ||
| Undiscounted lease liabilities | 241 | 270 |
| More than five years [member] | ||
| Disclosure of maturity analysis of operating lease payments [line items] | ||
| Undiscounted lease liabilities | £ 259 | £ 276 |