Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2021-12-31 |
As at 2020-12-31 |
As at 2020-01-01 |
As at 2019-12-31 |
|---|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | ||||
| Property, plant and equipment [abstract] | ||||
| Property, plant and equipment |
254,300,000
GBP
|
262,500,000
GBP
|
273,500,000
GBP
|
— |
| Intangible assets and goodwill [abstract] | ||||
| Intangible assets and goodwill |
483,500,000
GBP
|
502,400,000
GBP
|
481,900,000
GBP
|
— |
| Trade and other non-current receivables [abstract] | ||||
| Non-current trade receivables |
5,200,000
GBP
|
4,700,000
GBP
|
5,600,000
GBP
|
— |
| Miscellaneous non-current assets [abstract] | ||||
| Non-current net defined benefit asset |
34,100,000
GBP
|
12,600,000
GBP
|
16,900,000
GBP
|
— |
| Non-current derivative financial assets |
700,000
GBP
|
-
GBP
|
-
GBP
|
— |
| Trade and other current receivables [abstract] | ||||
| Trade and other current receivables |
175,200,000
GBP
|
154,200,000
GBP
|
166,900,000
GBP
|
— |
| Classes of current inventories [abstract] | ||||
| Current inventories |
128,700,000
GBP
|
102,600,000
GBP
|
113,100,000
GBP
|
— |
| Classes of current inventories, alternative [abstract] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents |
136,300,000
GBP
|
135,800,000
GBP
|
70,400,000
GBP
|
70,400,000
GBP
|
| Miscellaneous current assets [abstract] | ||||
| Current derivative financial assets |
500,000
GBP
|
300,000
GBP
|
800,000
GBP
|
— |
| Borrowings [abstract] | ||||
| Non-current portion of non-current borrowings |
31 3.3
GBP
|
285,200,000
GBP
|
249,000,000
GBP
|
— |
| Current borrowings and current portion of non-current borrowings [abstract] | ||||
| Current borrowings |
-
GBP
|
-
GBP
|
60,700,000
GBP
|
— |
| Non-current portion of non-current borrowings, by type [abstract] | ||||
| Trade and other non-current payables [abstract] | ||||
| Other non-current payables |
-
GBP
|
2,200,000
GBP
|
-
GBP
|
— |
| Trade and other current payables [abstract] | ||||
| Trade and other current payables |
180,900,000
GBP
|
155,400,000
GBP
|
174,500,000
GBP
|
— |
| Miscellaneous non-current liabilities [abstract] | ||||
| Non-current net defined benefit liability |
25,100,000
GBP
|
36,500,000
GBP
|
34,300,000
GBP
|
— |
| Miscellaneous current liabilities [abstract] | ||||
| Current derivative financial liabilities |
100,000
GBP
|
500,000
GBP
|
300,000
GBP
|
— |
| Issued capital [abstract] | ||||
| Issued capital |
75,600,000
GBP
|
75,600,000
GBP
|
66,000,000
GBP
|
— |
| Retained earnings [abstract] | ||||
| Retained earnings |
333,600,000
GBP
|
300,800,000
GBP
|
307,100,000
GBP
|
— |
| Accumulated other comprehensive income [abstract] | ||||
| Reserve of exchange differences on translation |
47,500,000
GBP
|
24,100,000
GBP
|
11,000,000
GBP
|
— |
| Reserve of cash flow hedges |
1,500,000
GBP
|
100,000
GBP
|
300,000
GBP
|
— |
| Miscellaneous equity [abstract] | ||||
| Capital redemption reserve |
100,000
GBP
|
100,000
GBP
|
100,000
GBP
|
— |
| Merger reserve |
385,200,000
GBP
|
385,200,000
GBP
|
298,100,000
GBP
|
— |
| Net assets (liabilities) [abstract] | ||||
| Assets |
1,282,000,000
GBP
|
1,252,100,000
GBP
|
1,200,900,000
GBP
|
— |
| Liabilities |
653,100,000
GBP
|
634,100,000
GBP
|
665,400,000
GBP
|
— |
| Net current assets (liabilities) [abstract] | ||||
| Current assets |
442,200,000
GBP
|
396,600,000
GBP
|
364,400,000
GBP
|
— |
| Current liabilities |
215,200,000
GBP
|
206,400,000
GBP
|
288,100,000
GBP
|
— |
| Assets less current liabilities [abstract] |