Related party transactions (Details) £ in Millions, $ in Millions |
6 Months Ended | ||
|---|---|---|---|
|
Sep. 30, 2026
GBP (£)
|
Sep. 30, 2026
USD ($)
|
Sep. 30, 2025
GBP (£)
|
|
| Disclosure of transactions between related parties [line items] | |||
| Purchase of investments other than investments accounted for using equity method | £ 979 | £ 44 | |
| Joulent LLC | |||
| Disclosure of transactions between related parties [line items] | |||
| Purchase of investments other than investments accounted for using equity method | £ 120 | $ 159 | |
| Joulent LLC | Investments held at fair value through profit and loss | |||
| Disclosure of transactions between related parties [line items] | |||
| Proportion of ownership interest in joint venture | 35.00% | 35.00% | |
| Joulent LLC | Investments held at fair value through profit and loss | Level 3 | |||
| Disclosure of transactions between related parties [line items] | |||
| Investments, capital contributions | £ 268 | $ 355 | |