Provisions - Schedule of environmental provision (Details) - GBP (£) £ in Millions |
12 Months Ended | ||
|---|---|---|---|
Mar. 31, 2024 |
Mar. 31, 2023 |
Mar. 31, 2022 |
|
| Disclosure of other provisions [line items] | |||
| Discounted | £ 3,109 | £ 2,642 | £ 2,539 |
| Environmental | |||
| Disclosure of other provisions [line items] | |||
| Discounted | 2,418 | 1,891 | £ 1,877 |
| Real undiscounted | 2,697 | £ 2,144 | |
| Real discount rate (in percent) | 1.50% | 0.50% | |
| Environmental | UK | |||
| Disclosure of other provisions [line items] | |||
| Discounted | 108 | £ 123 | |
| Real undiscounted | £ 118 | £ 138 | |
| Real discount rate (in percent) | 1.00% | 1.50% | |
| Environmental | US | |||
| Disclosure of other provisions [line items] | |||
| Discounted | £ 2,310 | £ 1,768 | |
| Real undiscounted | £ 2,579 | £ 2,006 | |
| Real discount rate (in percent) | 1.50% | 1.50% | |