Pensions and other post-retirement benefit obligations - Schedule of key actuarial assumptions (Details) |
Sep. 30, 2025 |
Mar. 31, 2025 |
|---|---|---|
| UK | ||
| Disclosure of defined benefit plans [line items] | ||
| Discount rate – UK past service | 5.76% | 5.73% |
| Rate of increase in RPI – UK past service | 2.81% | 2.99% |
| US | ||
| Disclosure of defined benefit plans [line items] | ||
| Discount rate – US | 5.30% | 5.50% |