Pensions and other post-retirement benefit obligations - Schedule of changes in restrictions on asset recognised (Details) - GBP (£) £ in Millions |
6 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Changes in restrictions on asset recognised [Roll Forward] | ||
| Opening restrictions on asset recognised at 1 April | £ (244) | |
| Closing restrictions on asset recognised at 30 September | (492) | |
| Post-employment medical defined benefit plans | US | ||
| Changes in restrictions on asset recognised [Roll Forward] | ||
| Opening restrictions on asset recognised at 1 April | (244) | £ (77) |
| Interest on restrictions on asset recognised | (9) | (5) |
| Other change in restrictions on asset recognised | (238) | (140) |
| Exchange adjustment on restrictions on asset recognised | (1) | 1 |
| Closing restrictions on asset recognised at 30 September | £ (492) | £ (221) |