Retirement benefit obligations - Schedule of Defined Benefit Scheme Obligations (Details) - GBP (£) £ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Disclosure of defined benefit plans [line items] | ||
| Total amounts recognised in the balance sheet | £ 2,744 | £ 2,575 |
| Retirement benefit assets | 2,860 | 2,695 |
| Retirement benefit obligations | (116) | (120) |
| Net pension scheme asset | ||
| Disclosure of defined benefit plans [line items] | ||
| Total amounts recognised in the balance sheet | 2,779 | 2,612 |
| Other post-retirement schemes | ||
| Disclosure of defined benefit plans [line items] | ||
| Total amounts recognised in the balance sheet | (35) | (37) |
| Present value of funded obligations | ||
| Disclosure of defined benefit plans [line items] | ||
| Total amounts recognised in the balance sheet | (25,483) | (26,571) |
| Fair value of scheme assets | ||
| Disclosure of defined benefit plans [line items] | ||
| Total amounts recognised in the balance sheet | £ 28,262 | £ 29,183 |