Statement Of Financial Position [Abstract]
| Concept |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||
| Assets [abstract] | |||||||||||||||
| Property, plant and equipment |
74,800,000
GBP
|
— | — | — | — |
66,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Investment property |
800,000
GBP
|
— | — | — | — |
800,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Cash and cash equivalents |
431,700,000
GBP
|
— | — | — | — |
468,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Assets |
1,794,400,000
GBP
|
— | — | — | — |
1,707,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Equity and liabilities [abstract] | |||||||||||||||
| Equity [abstract] | |||||||||||||||
| Issued capital |
2,400,000
GBP
|
— | — | — | — |
2,300,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Retained earnings |
436,800,000
GBP
|
— | — | — | — |
427,100,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Share premium |
55,900,000
GBP
|
— | — | — | — |
45,800,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Equity attributable to owners of parent |
496,200,000
GBP
|
— | — | — | — |
474,200,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Equity |
496,200,000
GBP
|
55,900,000
GBP
|
436,800,000
GBP
|
2,400,000
GBP
|
1,100,000
GBP
|
474,200,000
GBP
|
427,100,000
GBP
|
1,000,000
GBP
|
45,800,000
GBP
|
2,300,000
GBP
|
420,100,000
GBP
|
2,300,000
GBP
|
373,100,000
GBP
|
800,000
GBP
|
45,500,000
GBP
|
| Liabilities [abstract] | |||||||||||||||
| Deferred tax liabilities |
6,800,000
GBP
|
— | — | — | — |
10,000,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Liabilities |
1,298,200,000
GBP
|
— | — | — | — |
1,233,400,000
GBP
|
— | — | — | — | — | — | — | — | — |