Property, plant and equipment - Disclosure of sensitivity of gas assets (Details) - GBP (£) £ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2024 |
Mar. 31, 2023 |
|
| New York | ||
| Disclosure of operating segments [line items] | ||
| UELs limited to 2050, impact on depreciation expense | £ 208 | £ 185 |
| UELs limited to 2060, impact on depreciation expense | 100 | 90 |
| UELs limited to 2070, impact on depreciation expense | 46 | 42 |
| New England | ||
| Disclosure of operating segments [line items] | ||
| UELs limited to 2050, impact on depreciation expense | 66 | 54 |
| UELs limited to 2060, impact on depreciation expense | 26 | 21 |
| UELs limited to 2070, impact on depreciation expense | £ 6 | £ 3 |