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 2022-01-01 |
As at 2021-12-31 |
|---|---|---|---|---|---|---|
| Statement of cash flows [abstract] | ||||||
| Cash flows from (used in) operating activities [abstract] | ||||||
| Cash flows from (used in) operations |
412,000,000
GBP
|
— | — |
568,100,000
GBP
|
— | — |
| Interest received, classified as operating activities |
76,800,000
GBP
|
— | — |
58,700,000
GBP
|
— | — |
| Income taxes paid (refund), classified as operating activities |
133,000,000
GBP
|
— | — |
91,200,000
GBP
|
— | — |
| Cash flows from (used in) operating activities |
279,000,000
GBP
|
— | — |
476,900,000
GBP
|
— | — |
| Cash flows from (used in) investing activities [abstract] | ||||||
| Purchase of property, plant and equipment, classified as investing activities |
75,900,000
GBP
|
— | — |
98,600,000
GBP
|
— | — |
| Cash flows from (used in) investing activities |
75,900,000
GBP
|
— | — |
101,000,000
GBP
|
— | — |
| Cash flows from (used in) financing activities [abstract] | ||||||
| Payments of lease liabilities, classified as financing activities |
10,700,000
GBP
|
— | — |
9,200,000
GBP
|
— | — |
| Dividends paid, classified as financing activities |
307,100,000
GBP
|
— | — |
658,300,000
GBP
|
— | — |
| Interest paid, classified as financing activities |
35,100,000
GBP
|
— | — |
25,300,000
GBP
|
— | — |
| Cash flows from (used in) financing activities |
171,800,000
GBP
|
— | — |
425,000,000
GBP
|
— | — |
| Increase (decrease) in cash and cash equivalents before effect of exchange rate changes |
31,300,000
GBP
|
— | — |
49,100,000
GBP
|
— | — |
| Effect of exchange rate changes on cash and cash equivalents [abstract] | ||||||
| Effect of exchange rate changes on cash and cash equivalents |
24,800,000
GBP
|
— | — |
26,600,000
GBP
|
— | — |
| Cash and cash equivalents | — |
353,100,000
GBP
|
297,000,000
GBP
|
— |
372,700,000
GBP
|
372,700,000
GBP
|