Statement Of Cash Flows [Abstract]
| Concept |
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 |
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) | — |
–
GBP
|
–
GBP
|
19,200,000
GBP
|
19,200,000
GBP
|
19,200,000
GBP
|
20,300,000
GBP
|
— |
–
GBP
|
20,300,000
GBP
|
–
GBP
|
–
GBP
|
20,300,000
GBP
|
— |
| Adjustments to reconcile profit (loss) [abstract] | ||||||||||||||
| Adjustments for provisions | — | — | — | — |
–
GBP
|
— | — | — | — |
500,000
GBP
|
— | — | — | — |
| Adjustments for share-based payments | — | — | — | — |
1,500,000
GBP
|
— | — | — | — |
1,500,000
GBP
|
— | — | — | — |
| Cash flows from (used in) operations | — | — | — | — |
31,300,000
GBP
|
— | — | — | — |
30,100,000
GBP
|
— | — | — | — |
| Cash flows from (used in) operating activities | — | — | — | — |
26,700,000
GBP
|
— | — | — | — |
25,500,000
GBP
|
— | — | — | — |
| Cash flows from (used in) investing activities [abstract] | ||||||||||||||
| Purchase of property, plant and equipment, classified as investing activities | — | — | — | — |
300,000
GBP
|
— | — | — | — |
200,000
GBP
|
— | — | — | — |
| Interest received, classified as investing activities | — | — | — | — |
–
GBP
|
— | — | — | — |
100,000
GBP
|
— | — | — | — |
| Cash flows from (used in) investing activities | — | — | — | — |
1,300,000
GBP
|
— | — | — | — |
1,300,000
GBP
|
— | — | — | — |
| Cash flows from (used in) financing activities [abstract] | ||||||||||||||
| Payments to acquire or redeem entity's shares | — | — | — | — |
4,600,000
GBP
|
— | — | — | — |
–
GBP
|
— | — | — | — |
| Payments of lease liabilities, classified as financing activities | — | — | — | — |
1,900,000
GBP
|
— | — | — | — |
1,700,000
GBP
|
— | — | — | — |
| Cash flows from (used in) financing activities | — | — | — | — |
39,200,000
GBP
|
— | — | — | — |
45,900,000
GBP
|
— | — | — | — |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — | — | — | — |
13,800,000
GBP
|
— | — | — | — |
21,700,000
GBP
|
— | — | — | — |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | ||||||||||||||
| Effect of exchange rate changes on cash and cash equivalents | — | — | — | — |
100,000
GBP
|
— | — | — | — |
100,000
GBP
|
— | — | — | — |
| Cash and cash equivalents |
23,100,000
GBP
|
— | — | — | — | — | — |
37,000,000
GBP
|
— | — | — | — | — |
58,800,000
GBP
|