Segmental analysis - Schedule of geographical analysis of non-current assets (Details) - GBP (£) £ in Millions |
Sep. 30, 2025 |
Mar. 31, 2025 |
|---|---|---|
| Disclosure of operating segments [line items] | ||
| Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts | £ 90,878 | £ 88,754 |
| Pensions and other post-retirement benefit assets | 2,424 | 2,489 |
| Financial and other investments | 795 | 798 |
| Derivative financial assets | 736 | 369 |
| Total non-current assets | 94,833 | 92,410 |
| UK | ||
| Disclosure of operating segments [line items] | ||
| Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts | 44,625 | 42,623 |
| US | ||
| Disclosure of operating segments [line items] | ||
| Non-current assets other than financial instruments, deferred tax assets, post-employment benefit assets, and rights arising under insurance contracts | £ 46,253 | £ 46,131 |