Statement Of Cash Flows [Abstract]
| Concept |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
As at 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] | |||||
| Cash flows from (used in) operations | — |
294,800,000
GBP
|
— |
277,500,000
GBP
|
— |
| Income taxes paid (refund), classified as operating activities | — |
52,700,000
GBP
|
— |
53,200,000
GBP
|
— |
| Cash flows from (used in) operating activities | — |
242,100,000
GBP
|
— |
224,300,000
GBP
|
— |
| Cash flows from (used in) investing activities [abstract] | |||||
| Proceeds from sales of property, plant and equipment, classified as investing activities | — |
1,100,000
GBP
|
— |
7,500,000
GBP
|
— |
| Purchase of property, plant and equipment, classified as investing activities | — |
23,700,000
GBP
|
— |
18,800,000
GBP
|
— |
| Purchase of intangible assets, classified as investing activities | — |
11,800,000
GBP
|
— |
11,500,000
GBP
|
— |
| Interest received, classified as investing activities | — |
2,400,000
GBP
|
— |
300,000
GBP
|
— |
| Cash flows from (used in) investing activities | — |
60,300,000
GBP
|
— |
25,000,000
GBP
|
— |
| Cash flows from (used in) financing activities [abstract] | |||||
| Proceeds from issuing shares | — |
6,200,000
GBP
|
— |
6,200,000
GBP
|
— |
| Payments to acquire or redeem entity's shares | — |
34,400,000
GBP
|
— |
25,500,000
GBP
|
— |
| Proceeds from borrowings, classified as financing activities | — |
4,000,000
GBP
|
— |
10,700,000
GBP
|
— |
| Repayments of borrowings, classified as financing activities | — |
20,600,000
GBP
|
— |
99,700,000
GBP
|
— |
| Payments of lease liabilities, classified as financing activities | — |
50,300,000
GBP
|
— |
50,200,000
GBP
|
— |
| Interest paid, classified as financing activities | — |
2,900,000
GBP
|
— |
2,300,000
GBP
|
— |
| Cash flows from (used in) financing activities | — |
183,400,000
GBP
|
— |
228,400,000
GBP
|
— |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes | — |
1,600,000
GBP
|
— |
29,100,000
GBP
|
— |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | |||||
| Effect of exchange rate changes on cash and cash equivalents | — |
7,200,000
GBP
|
— |
7,500,000
GBP
|
— |
| Cash and cash equivalents |
264,400,000
GBP
|
— |
273,200,000
GBP
|
— |
309,800,000
GBP
|