Statement Of Changes In Equity [Abstract]
| Concept |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
2021-01-01 to 2021-12-31 |
2021-01-01 to 2021-12-31 |
As at 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 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 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 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of changes in equity [abstract] | |||||||||||||||||||||||||||||||||||
| Statement of changes in equity [line items] | |||||||||||||||||||||||||||||||||||
| Equity | — |
245,300,000
GBP
|
104,000,000
GBP
|
— | — |
361,600,000
GBP
|
356,900,000
GBP
|
4,700,000
GBP
|
— | — |
7. 6
GBP
|
— | — | — | — |
211,900,000
GBP
|
4,300,000
GBP
|
32 4. 1
GBP
|
7. 6
GBP
|
— | — |
104,600,000
GBP
|
— | — |
328,400,000
GBP
|
— | — | — | — |
377 .5
GBP
|
3 .1
GBP
|
158,400,000
GBP
|
380 .6
GBP
|
211,500,000
GBP
|
7. 6
GBP
|
| Changes in equity [abstract] | |||||||||||||||||||||||||||||||||||
| Comprehensive income [abstract] | |||||||||||||||||||||||||||||||||||
| Profit (loss) |
4,300,000
GBP
|
— | — |
–
GBP
|
50 .1
GBP
|
— | — | — |
–
GBP
|
54,700,000
GBP
|
— |
300,000
GBP
|
54,400,000
GBP
|
5 0 .1
GBP
|
25,800,000
GBP
|
— | — | — | — |
28,900,000
GBP
|
0 .4
GBP
|
— |
–
GBP
|
–
GBP
|
— |
3 .1
GBP
|
28,900,000
GBP
|
60,600,000
GBP
|
35,200,000
GBP
|
— | — | — | — | — | — |
| Other comprehensive income |
–
GBP
|
— | — |
2. 7
GBP
|
2,800,000
GBP
|
— | — | — |
–
GBP
|
— | — | — |
2,800,000
GBP
|
5,500,000
GBP
|
900,000
GBP
|
— | — | — | — |
1. 1
GBP
|
— | — |
0. 2
GBP
|
–
GBP
|
— |
–
GBP
|
900,000
GBP
|
— | — | — | — | — | — | — | — |
| Comprehensive income |
4,300,000
GBP
|
— | — |
2. 7
GBP
|
52,900,000
GBP
|
— | — | — |
–
GBP
|
— | — | — |
5 7. 2
GBP
|
55,600,000
GBP
|
26,700,000
GBP
|
— | — | — | — |
30,000,000
GBP
|
— | — |
0. 2
GBP
|
–
GBP
|
— |
3 .1
GBP
|
29,800,000
GBP
|
— | — | — | — | — | — | — | — |
| Issue of equity |
–
GBP
|
— | — |
1,800,000
GBP
|
1,800,000
GBP
|
— | — | — |
–
GBP
|
— | — | — |
1,800,000
GBP
|
–
GBP
|
600,000
GBP
|
— | — | — | — |
–
GBP
|
— | — |
600,000
GBP
|
–
GBP
|
— |
–
GBP
|
600,000
GBP
|
— | — | — | — | — | — | — | — |
| Dividends recognised as distributions to owners |
3,900,000
GBP
|
— | — |
–
GBP
|
24,400,000
GBP
|
— | — | — |
–
GBP
|
— | — | — |
28,300,000
GBP
|
24,400,000
GBP
|
25,500,000
GBP
|
— | — | — | — |
23,700,000
GBP
|
— | — |
–
GBP
|
–
GBP
|
— |
1,800,000
GBP
|
23. 7
GBP
|
— | — | — | — | — | — | — | — |
| Increase (decrease) through other changes, equity | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
–
GBP
|
— | — | — | — |
54,700,000
GBP
|
— | — |
54. 7
GBP
|
–
GBP
|
— |
–
GBP
|
–
GBP
|
— | — | — | — | — | — | — | — |
| Increase (decrease) through changes in ownership interests in subsidiaries that do not result in loss of control, equity | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
0. 1
GBP
|
— | — | — | — |
–
GBP
|
— | — |
–
GBP
|
–
GBP
|
— |
0. 1
GBP
|
–
GBP
|
— | — | — | — | — | — | — | — |
| Increase (decrease) through share-based payment transactions, equity |
–
GBP
|
— | — |
0. 3
GBP
|
200,000
GBP
|
— | — | — |
–
GBP
|
— | — | — |
200,000
GBP
|
0. 1
GBP
|
400,000
GBP
|
— | — | — | — |
500,000
GBP
|
— | — |
0 .1
GBP
|
–
GBP
|
— |
–
GBP
|
0 .4
GBP
|
— | — | — | — | — | — | — | — |