Statement Of Financial Position [Abstract]
| Concept |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2023-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2022-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
As at 2021-03-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | ||||||||||||||||||
| Assets [abstract] | ||||||||||||||||||
| Non-current assets [abstract] | ||||||||||||||||||
| Property, plant and equipment |
400,000
GBP
|
— | — | — | — | — | — | — | — | — |
900,000
GBP
|
— | — | — | — | — | — | — |
| Deferred tax assets |
–
GBP
|
— | — | — | — | — | — | — | — | — |
1,600,000
GBP
|
— | — | — | — | — | — | — |
| Non-current assets |
1,287,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
1,424,000,000
GBP
|
— | — | — | — | — | — | — |
| Current assets [abstract] | ||||||||||||||||||
| Trade and other current receivables |
5,000,000
GBP
|
— | — | — | — | — | — | — | — | — |
2,800,000
GBP
|
— | — | — | — | — | — | — |
| Cash and cash equivalents |
22,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
78,100,000
GBP
|
— | — | — | — |
160,700,000
GBP
|
— | — |
| Current assets |
27,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
80,900,000
GBP
|
— | — | — | — | — | — | — |
| Equity and liabilities [abstract] | ||||||||||||||||||
| Equity [abstract] | ||||||||||||||||||
| Issued capital |
1,500,000
GBP
|
— | — | — | — | — | — | — | — | — |
1,500,000
GBP
|
— | — | — | — | — | — | — |
| Retained earnings |
552,300,000
GBP
|
— | — | — | — | — | — | — | — | — |
795,700,000
GBP
|
— | — | — | — | — | — | — |
| Share premium |
615,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
615,900,000
GBP
|
— | — | — | — | — | — | — |
| Treasury shares |
8,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
8,200,000
GBP
|
— | — | — | — | — | — | — |
| Other reserves |
33,300,000
GBP
|
— | — | — | — | — | — | — | — | — |
28,900,000
GBP
|
— | — | — | — | — | — | — |
| Equity |
1,194,100,000
GBP
|
615,900,000
GBP
|
1,500,000
GBP
|
8,900,000
GBP
|
552,300,000
GBP
|
33,300,000
GBP
|
8,200,000
GBP
|
1,500,000
GBP
|
615,900,000
GBP
|
795,700,000
GBP
|
1,433,800,000
GBP
|
28,900,000
GBP
|
300,000
GBP
|
497,500,000
GBP
|
26,200,000
GBP
|
1,033,100,000
GBP
|
1,400,000
GBP
|
508,300,000
GBP
|
| Liabilities [abstract] | ||||||||||||||||||
| Non-current liabilities [abstract] | ||||||||||||||||||
| Non-current provisions [abstract] | ||||||||||||||||||
| Non-current provisions |
300,000
GBP
|
— | — | — | — | — | — | — | — | — |
300,000
GBP
|
— | — | — | — | — | — | — |
| Deferred tax liabilities |
22,500,000
GBP
|
— | — | — | — | — | — | — | — | — |
26,100,000
GBP
|
— | — | — | — | — | — | — |
| Non-current liabilities |
111,800,000
GBP
|
— | — | — | — | — | — | — | — | — |
56,400,000
GBP
|
— | — | — | — | — | — | — |
| Current liabilities [abstract] | ||||||||||||||||||
| Trade and other current payables |
9,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
14,300,000
GBP
|
— | — | — | — | — | — | — |
| Current liabilities |
9,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
14,700,000
GBP
|
— | — | — | — | — | — | — |