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 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 2020-12-31 |
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 |
As at 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of financial position [abstract] | |||||||||||||||||||||
| Assets [abstract] | |||||||||||||||||||||
| Non-current assets [abstract] | |||||||||||||||||||||
| Property, plant and equipment |
2 33 .7
GBP
|
— | — | — | — | — | — | — | — | — | — |
201,400,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Right-of-use assets |
18 .1
GBP
|
— | — | — | — | — | — | — | — | — | — |
16,500,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Non-current assets |
275 . 4
GBP
|
— | — | — | — | — | — | — | — | — | — |
235,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Current assets [abstract] | |||||||||||||||||||||
| Current inventories |
4 3. 0
GBP
|
— | — | — | — | — | — | — | — | — | — |
32,800,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Trade and other current receivables |
4 4. 3
GBP
|
— | — | — | — | — | — | — | — | — | — |
39,100,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Cash and cash equivalents |
3 4. 3
GBP
|
— | — | — | — | — | — | — | — | — | — |
41,500,000
GBP
|
— | — | — | — | — | — | — |
31,500,000
GBP
|
— |
| Current assets |
12 2 . 2
GBP
|
— | — | — | — | — | — | — | — | — | — |
114,400,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Assets |
3 9 7. 6
GBP
|
— | — | — | — | — | — | — | — | — | — |
350,000,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Equity and liabilities [abstract] | |||||||||||||||||||||
| Equity [abstract] | |||||||||||||||||||||
| Issued capital |
2 .1
GBP
|
— | — | — | — | — | — | — | — | — | — |
2,300,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Retained earnings |
23 3 .4
GBP
|
— | — | — | — | — | — | — | — | — | — |
213,400,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Treasury shares |
15 . 8
GBP
|
— | — | — | — | — | — | — | — | — | — |
4,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Other reserves |
–
GBP
|
— | — | — | — | — | — | — | — | — | — |
23,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Equity |
2 20 . 5
GBP
|
–
GBP
|
0. 2
GBP
|
2 3 3. 4
GBP
|
15 . 8
GBP
|
2 .1
GBP
|
600,000
GBP
|
4,600,000
GBP
|
213,400,000
GBP
|
–
GBP
|
23,900,000
GBP
|
234,800,000
GBP
|
200,000
GBP
|
2,300,000
GBP
|
162,300,000
GBP
|
–
GBP
|
2,300,000
GBP
|
2,000,000
GBP
|
41,500,000
GBP
|
204,100,000
GBP
|
–
GBP
|
| Liabilities [abstract] | |||||||||||||||||||||
| Non-current liabilities [abstract] | |||||||||||||||||||||
| Non-current provisions [abstract] | |||||||||||||||||||||
| Non-current provisions |
10 .0
GBP
|
— | — | — | — | — | — | — | — | — | — |
9,700,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Deferred tax liabilities |
5. 0
GBP
|
— | — | — | — | — | — | — | — | — | — |
2,700,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Non-current liabilities |
6 8 . 3
GBP
|
— | — | — | — | — | — | — | — | — | — |
24,400,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Current liabilities [abstract] | |||||||||||||||||||||
| Current provisions [abstract] | |||||||||||||||||||||
| Current provisions |
14 . 3
GBP
|
— | — | — | — | — | — | — | — | — | — |
9,900,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Trade and other current payables |
8 9 .6
GBP
|
— | — | — | — | — | — | — | — | — | — |
75,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Current liabilities |
10 8 . 8
GBP
|
— | — | — | — | — | — | — | — | — | — |
90,800,000
GBP
|
— | — | — | — | — | — | — | — | — |
| Liabilities |
17 7. 1
GBP
|
— | — | — | — | — | — | — | — | — | — |
115,200,000
GBP
|
— | — | — | — | — | — | — | — | — |