Statement Of Financial Position [Abstract]
| Concept |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
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 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 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | ||||||||||||||||||||||||
| Assets [abstract] | ||||||||||||||||||||||||
| Non-current assets [abstract] | ||||||||||||||||||||||||
| Property, plant and equipment |
16,000,000
GBP
|
— | — | — | — | — | — | — |
17,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Right-of-use assets |
21,700,000
GBP
|
— | — | — | — | — | — | — |
19,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Goodwill |
23,600,000
GBP
|
— | — | — | — | — | — | — |
24,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Intangible assets other than goodwill |
32,300,000
GBP
|
— | — | — | — | — | — | — |
27,900,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Trade and other non-current receivables |
203,300,000
GBP
|
— | — | — | — | — | — | — |
212,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Deferred tax assets |
131,700,000
GBP
|
— | — | — | — | — | — | — |
138,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Non-current assets |
434,700,000
GBP
|
— | — | — | — | — | — | — |
441,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Current assets [abstract] | ||||||||||||||||||||||||
| Trade and other current receivables |
689,600,000
GBP
|
— | — | — | — | — | — | — |
656,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Current tax assets, current |
3,300,000
GBP
|
— | — | — | — | — | — | — |
1,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Cash and cash equivalents |
42,500,000
GBP
|
— | — | — | — | — | — | — |
50,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
41,700,000
GBP
|
— | — | — |
| Current assets |
754,300,000
GBP
|
— | — | — | — | — | — | — |
729,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Assets |
1,189,000,000
GBP
|
— | — | — | — | — | — | — |
1,171,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Equity and liabilities [abstract] | ||||||||||||||||||||||||
| Equity [abstract] | ||||||||||||||||||||||||
| Issued capital |
23,400,000
GBP
|
— | — | — | — | — | — | — |
23,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Retained earnings |
503,200,000
GBP
|
— | — | — | — | — | — | — |
476,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Treasury shares |
36,700,000
GBP
|
— | — | — | — | — | — | — |
43,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Other reserves |
22,500,000
GBP
|
— | — | — | — | — | — | — |
22,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Equity |
501,900,000
GBP
|
503. 2
GBP
|
2. 3
GBP
|
22,500,000
GBP
|
23,400,000
GBP
|
32,000,000
GBP
|
36,700,000
GBP
|
200,000
GBP
|
445,200,000
GBP
|
22,500,000
GBP
|
2,300,000
GBP
|
476,000,000
GBP
|
43,300,000
GBP
|
23,400,000
GBP
|
9,200,000
GBP
|
100,000
GBP
|
46,600,000
GBP
|
441,500,000
GBP
|
2,300,000
GBP
|
22,500,000
GBP
|
367,100,000
GBP
|
1,600,000
GBP
|
32,600,000
GBP
|
23,400,000
GBP
|
| Liabilities [abstract] | ||||||||||||||||||||||||
| Non-current liabilities [abstract] | ||||||||||||||||||||||||
| Deferred tax liabilities |
7,100,000
GBP
|
— | — | — | — | — | — | — |
5. 9
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Non-current liabilities |
482,000,000
GBP
|
— | — | — | — | — | — | — |
497,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Current liabilities [abstract] | ||||||||||||||||||||||||
| Current provisions [abstract] | ||||||||||||||||||||||||
| Current provisions |
–
GBP
|
— | — | — | — | — | — | — |
4,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Trade and other current payables |
132,900,000
GBP
|
— | — | — | — | — | — | — |
122,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Current liabilities |
205,100,000
GBP
|
— | — | — | — | — | — | — |
228,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Liabilities |
687,100,000
GBP
|
— | — | — | — | — | — | — |
725,900,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |