Operating Expenses - Summary of Reconciliation Between Audit and Non-Audit Service Fees (Detail) - GBP (£) £ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Auditor's remuneration [abstract] | |||
| Group audit fees including fees for attestation under section 404 of the Sarbanes-Oxley Act | £ 9 | £ 9 | £ 10 |
| Non-audit fees | 0 | 0 | 0 |
| Total | £ 9 | £ 9 | £ 10 |