Retirement benefit obligations - Schedule of Retirement Benefit Total Amounts Recognized in Balance Sheet (Details) - GBP (£) £ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|---|
| RETIREMENT BENEFIT OBLIGATIONS (Details) - Schedule of Retirement Benefit Total Amounts Recognized in Balance Sheet [Line Items] | |||
| Retirement benefit assets | £ 2,695 | £ 3,028 | |
| Retirement benefit obligations | (120) | (122) | |
| Defined benefit asset | 2,575 | 2,906 | |
| Defined benefit pension schemes | |||
| RETIREMENT BENEFIT OBLIGATIONS (Details) - Schedule of Retirement Benefit Total Amounts Recognized in Balance Sheet [Line Items] | |||
| Retirement benefit assets | 2,695 | 3,028 | |
| Retirement benefit obligations | (83) | (83) | |
| Defined benefit asset | 2,612 | 2,945 | £ 3,532 |
| Other retirement benefit schemes | |||
| RETIREMENT BENEFIT OBLIGATIONS (Details) - Schedule of Retirement Benefit Total Amounts Recognized in Balance Sheet [Line Items] | |||
| Defined benefit asset | £ (37) | £ (39) |