Derivative financial instruments - Schedule of notional contract amounts of financing derivatives by type (Details) - GBP (£) £ in Millions |
Mar. 31, 2024 |
Mar. 31, 2023 |
|---|---|---|
| Financing derivatives | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Derivative notional amount | £ (28,642) | £ (24,402) |
| Interest rate swaps | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Derivative notional amount | (2,175) | (1,727) |
| Cross-currency interest rate swaps | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Derivative notional amount | (15,602) | (15,025) |
| Foreign exchange forward contracts | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Derivative notional amount | (7,675) | (5,263) |
| Inflation-linked swaps | ||
| Disclosure of detailed information about financial instruments [line items] | ||
| Derivative notional amount | £ (3,190) | £ (2,387) |