Statement Of Cash Flows [Abstract]
| Concept |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2019-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of cash flows [abstract] | ||||||||||||||||||||
| Cash flows from (used in) operating activities [abstract] | ||||||||||||||||||||
| Profit (loss) |
4,300,000
GBP
|
–
GBP
|
50 .1
GBP
|
— |
300,000
GBP
|
–
GBP
|
54,700,000
GBP
|
54,400,000
GBP
|
5 0 .1
GBP
|
25,800,000
GBP
|
28,900,000
GBP
|
0 .4
GBP
|
–
GBP
|
— |
–
GBP
|
3 .1
GBP
|
28,900,000
GBP
|
60,600,000
GBP
|
35,200,000
GBP
|
— |
| Adjustments to reconcile profit (loss) [abstract] | ||||||||||||||||||||
| Adjustments for finance costs | — | — | — | — | — | — | — |
3 .1
GBP
|
— |
3 .1
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Adjustments for decrease (increase) in inventories | — | — | — | — | — | — | — |
200,000
GBP
|
— |
200,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Adjustments for decrease (increase) in trade accounts receivable | — | — | — | — | — | — | — |
38,700,000
GBP
|
— |
0. 3
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Adjustments for increase (decrease) in trade accounts payable | — | — | — | — | — | — | — |
2 9 .1
GBP
|
— |
3,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Adjustments for provisions | — | — | — | — | — | — | — |
0 .1
GBP
|
— |
200,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Adjustments for share-based payments | — | — | — | — | — | — | — |
1,800,000
GBP
|
— |
1,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) operations | — | — | — | — | — | — | — |
123,000,000
GBP
|
— |
76,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Income taxes paid (refund), classified as operating activities | — | — | — | — | — | — | — |
9,200,000
GBP
|
— |
10 .7
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) operating activities | — | — | — | — | — | — | — |
113,800,000
GBP
|
— |
65,900,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) investing activities [abstract] | ||||||||||||||||||||
| Proceeds from sales of property, plant and equipment, classified as investing activities | — | — | — | — | — | — | — |
1,600,000
GBP
|
— |
0. 4
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Purchase of property, plant and equipment, classified as investing activities | — | — | — | — | — | — | — |
3,700,000
GBP
|
— |
3,500,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Purchase of intangible assets, classified as investing activities | — | — | — | — | — | — | — |
2,900,000
GBP
|
— |
6,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Dividends received, classified as investing activities | — | — | — | — | — | — | — |
–
GBP
|
— |
200,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Interest received, classified as investing activities | — | — | — | — | — | — | — |
200,000
GBP
|
— |
500,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) investing activities | — | — | — | — | — | — | — |
14,300,000
GBP
|
— |
28. 1
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) financing activities [abstract] | ||||||||||||||||||||
| Payments from changes in ownership interests in subsidiaries that do not result in loss of control | — | — | — | — | — | — | — |
–
GBP
|
— |
0 . 1
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Proceeds from issuing shares | — | — | — | — | — | — | — |
1,800,000
GBP
|
— |
0. 6
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Repayments of borrowings, classified as financing activities | — | — | — | — | — | — | — |
0. 1
GBP
|
— |
1,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Payments of lease liabilities, classified as financing activities | — | — | — | — | — | — | — |
9. 1
GBP
|
— |
8,900,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Interest paid, classified as financing activities | — | — | — | — | — | — | — |
2,300,000
GBP
|
— |
2,700,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash flows from (used in) financing activities | — | — | — | — | — | — | — |
39,900,000
GBP
|
— |
37 .9
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — | — | — | — | — | — | — |
88,200,000
GBP
|
— |
0. 1
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | ||||||||||||||||||||
| Effect of exchange rate changes on cash and cash equivalents | — | — | — | — | — | — | — |
–
GBP
|
— |
2,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — |
| Cash and cash equivalents | — | — | — |
261,600,000
GBP
|
— | — | — | — | — | — | — | — | — |
17 3.4
GBP
|
— | — | — | — | — |
175,700,000
GBP
|