Statement Of Cash Flows [Abstract]
| Concept |
As at 2025-03-31 |
2024-04-01 to 2025-03-31 |
2023-04-01 to 2024-03-31 |
As at 2024-03-31 |
As at 2023-03-31 |
|---|---|---|---|---|---|
| Statement of cash flows [abstract] | |||||
| Cash flows from (used in) operating activities [abstract] | |||||
| Classes of cash receipts from operating activities [abstract] | |||||
| Other cash receipts from operating activities | — |
1,000,000
GBP
|
2,000,000
GBP
|
— | — |
| Classes of cash payments from operating activities [abstract] | |||||
| Other cash payments from operating activities | — |
10,000,000
GBP
|
–
GBP
|
— | — |
| Interest received, classified as operating activities | — |
15,000,000
GBP
|
9,000,000
GBP
|
— | — |
| Income taxes paid (refund), classified as operating activities | — |
3,000,000
GBP
|
3,000,000
GBP
|
— | — |
| Cash flows from (used in) operating activities | — |
763,000,000
GBP
|
366,000,000
GBP
|
— | — |
| Cash flows from (used in) investing activities [abstract] | |||||
| Purchase of property, plant and equipment, classified as investing activities | — |
16,000,000
GBP
|
3,000,000
GBP
|
— | — |
| Cash flows from (used in) investing activities | — |
16,000,000
GBP
|
3,000,000
GBP
|
— | — |
| Cash flows from (used in) financing activities [abstract] | |||||
| Proceeds from issuing shares | — |
1,000,000
GBP
|
1,000,000
GBP
|
— | — |
| Payments of lease liabilities, classified as financing activities | — |
6,000,000
GBP
|
6,000,000
GBP
|
— | — |
| Dividends paid, classified as financing activities | — |
625,000,000
GBP
|
541,000,000
GBP
|
— | — |
| Interest paid, classified as financing activities | — |
60,000,000
GBP
|
40,000,000
GBP
|
— | — |
| Cash flows from (used in) financing activities | — |
690,000,000
GBP
|
164,000,000
GBP
|
— | — |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — |
57,000,000
GBP
|
199,000,000
GBP
|
— | — |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents | — |
3,000,000
GBP
|
3,000,000
GBP
|
— | — |
| Cash and cash equivalents |
412,000,000
GBP
|
— | — |
358,000,000
GBP
|
162,000,000
GBP
|