Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2025-03-31 |
As at 2024-03-31 |
As at 2023-03-31 |
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment |
18,000,000
GBP
|
4,000,000
GBP
|
— |
| Intangible assets and goodwill [abstract] | |||
| Intangible assets other than goodwill [abstract] | |||
| Intangible assets other than goodwill |
2,000,000
GBP
|
4,000,000
GBP
|
— |
| Investments in subsidiaries, joint ventures and associates reported in separate financial statements [abstract] | |||
| Investments in subsidiaries reported in separate financial statements |
6,916,000,000
GBP
|
5,804,000,000
GBP
|
— |
| Miscellaneous non-current assets [abstract] | |||
| Non-current net defined benefit asset |
63,000,000
GBP
|
61,000,000
GBP
|
— |
| Non-current derivative financial assets |
46,000,000
GBP
|
83,000,000
GBP
|
— |
| Other non-current assets |
27,000,000
GBP
|
28,000,000
GBP
|
— |
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents |
412,000,000
GBP
|
358,000,000
GBP
|
162,000,000
GBP
|
| Miscellaneous current assets [abstract] | |||
| Current derivative financial assets |
91,000,000
GBP
|
82,000,000
GBP
|
— |
| Other current assets |
49,000,000
GBP
|
47,000,000
GBP
|
— |
| Borrowings [abstract] | |||
| Non-current portion of non-current borrowings |
1,194,000,000
GBP
|
1,202,000,000
GBP
|
— |
| Non-current portion of non-current borrowings, by type [abstract] | |||
| Trade and other non-current payables [abstract] | |||
| Trade and other non-current payables |
6,000,000
GBP
|
5,000,000
GBP
|
— |
| Trade and other current payables [abstract] | |||
| Trade and other current payables |
133,000,000
GBP
|
134,000,000
GBP
|
— |
| Miscellaneous non-current liabilities [abstract] | |||
| Non-current net defined benefit liability |
17,000,000
GBP
|
21,000,000
GBP
|
— |
| Non-current derivative financial liabilities |
4,000,000
GBP
|
–
GBP
|
— |
| Issued capital [abstract] | |||
| Issued capital |
719,000,000
GBP
|
719,000,000
GBP
|
— |
| Retained earnings [abstract] | |||
| Retained earnings |
1,845,000,000
GBP
|
1,519,000,000
GBP
|
— |
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation |
1,000,000
GBP
|
6,000,000
GBP
|
— |
| Miscellaneous equity [abstract] | |||
| Reserve of share-based payments |
35,000,000
GBP
|
42,000,000
GBP
|
— |
| Capital redemption reserve |
43,000,000
GBP
|
43,000,000
GBP
|
— |
| Capital reserve |
21,257,000,000
GBP
|
17,154,000,000
GBP
|
— |
| Net assets (liabilities) [abstract] | |||
| Assets |
26,056,000,000
GBP
|
21,641,000,000
GBP
|
— |
| Liabilities |
1,445,000,000
GBP
|
1,471,000,000
GBP
|
— |
| Assets (liabilities) |
24,611,000,000
GBP
|
20,170,000,000
GBP
|
— |
| Net current assets (liabilities) [abstract] | |||
| Current assets |
587,000,000
GBP
|
533,000,000
GBP
|
— |
| Current liabilities |
150,000,000
GBP
|
165,000,000
GBP
|
— |
| Assets less current liabilities [abstract] |