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 |
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 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||||||||||||
| Profit (loss) |
–
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
34 6.9
GBP
|
346. 9
GBP
|
1 7. 0
GBP
|
–
GBP
|
1 7. 0
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
–
GBP
|
–
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) from investments in equity instruments | — | — | — | — | — | — |
1 .8
GBP
|
— | — | — |
100,000
GBP
|
— | — | — | — | — |
| Other comprehensive income, before tax, gains (losses) on remeasurements of defined benefit plans | — | — | — | — | — | — |
1. 8
GBP
|
— | — | — |
8,500,000
GBP
|
— | — | — | — | — |
| Components of other comprehensive income that will be reclassified to profit or loss, before tax [abstract] | ||||||||||||||||
| Cash flow hedges [abstract] | ||||||||||||||||
| Other comprehensive income, before tax, cash flow hedges | — | — | — | — | — | — |
1 . 9
GBP
|
— | — | — |
600,000
GBP
|
— | — | — | — | — |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||||||||||||
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss | — | — | — | — | — | — |
0 .7
GBP
|
— | — | — |
1 . 3
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 | — | — | — | — | — | — |
0. 3
GBP
|
— | — | — |
0 .1
GBP
|
— | — | — | — | — |
| Other comprehensive income |
–
GBP
|
–
GBP
|
1 . 6
GBP
|
–
GBP
|
31 .8
GBP
|
–
GBP
|
34,400,000
GBP
|
1 .0
GBP
|
7. 3
GBP
|
–
GBP
|
6,200,000
GBP
|
600,000
GBP
|
–
GBP
|
0. 5
GBP
|
–
GBP
|
–
GBP
|
| Comprehensive income |
–
GBP
|
–
GBP
|
1 .6
GBP
|
–
GBP
|
31 .8
GBP
|
–
GBP
|
3 12.5
GBP
|
34 5.9
GBP
|
9 .7
GBP
|
–
GBP
|
10. 8
GBP
|
0. 6
GBP
|
–
GBP
|
0. 5
GBP
|
–
GBP
|
–
GBP
|