Statement Of Comprehensive Income [Abstract]
| Concept |
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 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||
| Profit (loss) |
254,125,000
GBP
|
254,125,000
GBP
|
254,125,000
GBP
|
76,813,000
GBP
|
76,813,000
GBP
|
76,813,000
GBP
|
| Other comprehensive income [abstract] | ||||||
| Components of other comprehensive income that will not be reclassified to profit or loss, before tax [abstract] | ||||||
| Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans | — |
33,838,000
GBP
|
— | — |
11,654,000
GBP
|
— |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||
| Income tax relating to remeasurements of defined benefit plans included in other comprehensive income | — |
9,148,000
GBP
|
— | — |
2,124,000
GBP
|
— |
| Other comprehensive income |
24,690,000
GBP
|
24,690,000
GBP
|
24,690,000
GBP
|
9,530,000
GBP
|
9,530,000
GBP
|
9,530,000
GBP
|
| Comprehensive income attributable to [abstract] | ||||||
| Comprehensive income, attributable to owners of parent |
278,815,000
GBP
|
278,815,000
GBP
|
278,815,000
GBP
|
67,283,000
GBP
|
67,283,000
GBP
|
67,283,000
GBP
|