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 |
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 |
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) | — | — | — | — |
263,200,000
GBP
|
263,200,000
GBP
|
185,900,000
GBP
|
186,300,000
GBP
|
— |
400,000
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 | — | — | — | — |
900,000
GBP
|
0. 9
GBP
|
13. 1
GBP
|
13. 1
GBP
|
— | — | — | — |
| Components of other comprehensive income that will be reclassified to profit or loss, before tax [abstract] | ||||||||||||
| Exchange differences on translation [abstract] | ||||||||||||
| Other comprehensive income, before tax, exchange differences on translation of foreign operations | — | — | — | — |
17 . 7
GBP
|
— | — |
35,400,000
GBP
|
— | — | — | — |
| Cash flow hedges [abstract] | ||||||||||||
| Other comprehensive income, before tax, cash flow hedges | — | — | — | — |
13,200,000
GBP
|
— | — |
4,900,000
GBP
|
— | — | — | — |
| Hedges of net investment in foreign operations [abstract] | ||||||||||||
| Other comprehensive income, before tax, hedges of net investments in foreign operations | — | — | — | — |
15,000,000
GBP
|
— | — |
17 .2
GBP
|
— | — | — | — |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||||||||
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss | — | — | — | — |
2,000,000
GBP
|
2,000,000
GBP
|
3,900,000
GBP
|
3,900,000
GBP
|
— | — | — | — |
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss [abstract] | ||||||||||||
| Income tax relating to components of other comprehensive income that will be reclassified to profit or loss | — | — | — | — |
4 .6
GBP
|
4,600,000
GBP
|
3,200,000
GBP
|
3,200,000
GBP
|
— | — | — | — |
| Other comprehensive income | — | — | — | — |
11,900,000
GBP
|
— | — |
67 . 7
GBP
|
— | — | — | — |
| Comprehensive income |
1,500,000
GBP
|
13,200,000
GBP
|
10,400,000
GBP
|
2. 7
GBP
|
275. 1
GBP
|
276,500,000
GBP
|
176. 7
GBP
|
118,600,000
GBP
|
52,600,000
GBP
|
0. 4
GBP
|
4,900,000
GBP
|
1,000,000
GBP
|