Statement Of Cash Flows [Abstract]
| Concept |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
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 |
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 |
As at 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of cash flows [abstract] | |||||||||||||||||||
| Cash flows from (used in) operating activities [abstract] | |||||||||||||||||||
| Profit (loss) | — |
–
GBP
|
–
GBP
|
–
GBP
|
47,900,000
GBP
|
47,300,000
GBP
|
600,000
GBP
|
47,300,000
GBP
|
–
GBP
|
200,000
GBP
|
–
GBP
|
–
GBP
|
149,400,000
GBP
|
— |
–
GBP
|
–
GBP
|
149,600,000
GBP
|
149,400,000
GBP
|
— |
| Cash flows from (used in) operations | — | — | — | — |
175,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
237,500,000
GBP
|
— | — |
| Income taxes paid (refund), classified as operating activities | — | — | — | — |
12,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
48,600,000
GBP
|
— | — |
| Cash flows from (used in) operating activities | — | — | — | — |
162,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
188,900,000
GBP
|
— | — |
| Cash flows from (used in) investing activities [abstract] | |||||||||||||||||||
| Purchase of property, plant and equipment, classified as investing activities | — | — | — | — |
1,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
1,400,000
GBP
|
— | — |
| Purchase of intangible assets, classified as investing activities | — | — | — | — |
4,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
2,100,000
GBP
|
— | — |
| Dividends received, classified as investing activities | — | — | — | — |
1,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
1,100,000
GBP
|
— | — |
| Cash flows from (used in) investing activities | — | — | — | — |
35,100,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
12,000,000
GBP
|
— | — |
| Cash flows from (used in) financing activities [abstract] | |||||||||||||||||||
| Payments of lease liabilities, classified as financing activities | — | — | — | — |
7,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
5,200,000
GBP
|
— | — |
| Dividends paid, classified as financing activities | — | — | — | — |
90,200,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
109,800,000
GBP
|
— | — |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — | — | — | — |
117,000,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
167,700,000
GBP
|
— | — |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||||||||||||||||
| Effect of exchange rate changes on cash and cash equivalents | — | — | — | — |
2,600,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
-
GBP
|
— | — |
| Increase (decrease) in cash and cash equivalents after effect of exchange rate changes | — | — | — | — |
80,400,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — |
9,200,000
GBP
|
— | — |
| Cash and cash equivalents |
280,300,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — |
197,300,000
GBP
|
— | — | — | — |
188,100,000
GBP
|