Statement Of Cash Flows [Abstract]
| Concept |
2023-01-01 to 2023-12-31 |
As at 2023-12-31 |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
As at 2021-12-31 |
|---|---|---|---|---|---|
| Statement of cash flows [abstract] | |||||
| Cash flows from (used in) operating activities [abstract] | |||||
| Cash flows from (used in) operations |
109,100,000
GBP
|
— | — |
175,100,000
GBP
|
— |
| Income taxes paid (refund), classified as operating activities |
21,100,000
GBP
|
— | — |
12,800,000
GBP
|
— |
| Cash flows from (used in) operating activities |
88,000,000
GBP
|
— | — |
162,300,000
GBP
|
— |
| Cash flows from (used in) investing activities [abstract] | |||||
| Purchase of property, plant and equipment, classified as investing activities |
600,000
GBP
|
— | — |
1,200,000
GBP
|
— |
| Purchase of intangible assets, classified as investing activities |
2,900,000
GBP
|
— | — |
4,100,000
GBP
|
— |
| Dividends received, classified as investing activities |
5,400,000
GBP
|
— | — |
1,000,000
GBP
|
— |
| Cash flows from (used in) investing activities |
56,600,000
GBP
|
— | — |
35,100,000
GBP
|
— |
| Cash flows from (used in) financing activities [abstract] | |||||
| Payments of lease liabilities, classified as financing activities |
4,900,000
GBP
|
— | — |
7,800,000
GBP
|
— |
| Dividends paid, classified as financing activities |
35,200,000
GBP
|
— | — |
90,200,000
GBP
|
— |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes |
42,400,000
GBP
|
— | — |
117,000,000
GBP
|
— |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents |
1,100,000
GBP
|
— | — |
2,600,000
GBP
|
— |
| Increase (decrease) in cash and cash equivalents after effect of exchange rate changes |
11,000,000
GBP
|
— | — |
80,400,000
GBP
|
— |
| Cash and cash equivalents | — |
268,200,000
GBP
|
280,300,000
GBP
|
— |
197,300,000
GBP
|