Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2023-12-31 |
As at 2022-12-31 |
As at 2021-12-31 |
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment |
28,500,000
GBP
|
25 .5
GBP
|
— |
| Intangible assets and goodwill [abstract] | |||
| Intangible assets and goodwill |
1 82.9
GBP
|
188 .9
GBP
|
— |
| Investment property [abstract] | |||
| Investment property |
1 .0
GBP
|
1 .0
GBP
|
— |
| Trade and other non-current receivables [abstract] | |||
| Trade and other non-current receivables |
4,400,000
GBP
|
2,600,000
GBP
|
— |
| Miscellaneous non-current assets [abstract] | |||
| Non-current net defined benefit asset |
13 .8
GBP
|
15. 8
GBP
|
— |
| Non-current investments other than investments accounted for using equity method |
1,300,000
GBP
|
1. 2
GBP
|
— |
| Trade and other current receivables [abstract] | |||
| Trade and other current receivables |
1 4 7. 5
GBP
|
150,100,000
GBP
|
— |
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents |
398,900,000
GBP
|
384,400,000
GBP
|
26 1.6
GBP
|
| Miscellaneous current assets [abstract] | |||
| Current investments |
4 0.1
GBP
|
3,500,000
GBP
|
— |
| Trade and other non-current payables [abstract] | |||
| Trade and other non-current payables |
3 . 2
GBP
|
5 . 8
GBP
|
— |
| Trade and other current payables [abstract] | |||
| Trade and other current payables |
3 3 9 .4
GBP
|
3 3 5 . 9
GBP
|
— |
| Miscellaneous non-current liabilities [abstract] | |||
| Non-current net defined benefit liability |
0 . 4
GBP
|
0 . 4
GBP
|
— |
| Issued capital [abstract] | |||
| Issued capital |
7. 7
GBP
|
7. 7
GBP
|
— |
| Retained earnings [abstract] | |||
| Retained earnings |
340,000,000
GBP
|
2 8 7. 2
GBP
|
— |
| Net assets (liabilities) [abstract] | |||
| Assets (liabilities) |
456 .6
GBP
|
41 3 . 2
GBP
|
— |
| Net current assets (liabilities) [abstract] | |||
| Current assets |
591,000,000
GBP
|
543. 4
GBP
|
— |
| Current liabilities |
37 1. 3
GBP
|
36 6 . 2
GBP
|
— |
| Current assets (liabilities) |
219,700,000
GBP
|
1 7 7. 2
GBP
|
— |
| Assets less current liabilities [abstract] |