Statement Of Changes In Equity [Abstract]
| Concept |
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 |
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 |
As at 2021-12-31 |
As at 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 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
2020-01-01 to 2020-12-31 |
As at 2020-12-31 |
As at 2020-12-31 |
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 |
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 |
As at 2019-12-31 |
As at 2019-12-31 |
As at 2019-12-31 |
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| Statement of changes in equity [abstract] | |||||||||||||||||||||||||||||||||||||||||||||
| Statement of changes in equity [line items] | |||||||||||||||||||||||||||||||||||||||||||||
| Equity | — |
6. 2
GBP
|
31 9.4
GBP
|
1 3 7. 5
GBP
|
— | — | — |
6 85.4
GBP
|
— | — |
6 8 4 .7
GBP
|
1 7 7.1
GBP
|
— |
23 .8
GBP
|
3 3 .1
GBP
|
0 .7
GBP
|
— | — | — |
3 06 .7
GBP
|
0. 9
GBP
|
— |
3 3 .1
GBP
|
68 0.5
GBP
|
— |
6. 9
GBP
|
3 7. 9
GBP
|
13 2 .6
GBP
|
1 7 7.1
GBP
|
— | — |
6 8 1. 4
GBP
|
— | — | — | — |
70 5. 0
GBP
|
0. 8
GBP
|
13 6 .7
GBP
|
3 7. 9
GBP
|
17 7. 1
GBP
|
70 5. 8
GBP
|
3 3 1. 8
GBP
|
11 . 6
GBP
|
3 3 .1
GBP
|
| Changes in equity [abstract] | |||||||||||||||||||||||||||||||||||||||||||||
| Comprehensive income [abstract] | |||||||||||||||||||||||||||||||||||||||||||||
| Profit (loss) |
0. 5
GBP
|
— | — | — |
–
GBP
|
–
GBP
|
5 9.5
GBP
|
— |
–
GBP
|
–
GBP
|
— | — |
–
GBP
|
— | — | — |
6 0.0
GBP
|
5 9.5
GBP
|
0 .8
GBP
|
— | — |
–
GBP
|
— | — |
0 .4
GBP
|
— | — | — | — |
–
GBP
|
–
GBP
|
— |
–
GBP
|
0. 4
GBP
|
–
GBP
|
0. 4
GBP
|
— | — | — | — | — | — | — | — | — |
| Other comprehensive income | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
12 . 0
GBP
|
— |
0 .1
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Comprehensive income |
0. 2
GBP
|
— | — | — |
–
GBP
|
1. 0
GBP
|
4 8. 2
GBP
|
— |
–
GBP
|
1 4 .1
GBP
|
— | — |
–
GBP
|
— | — | — |
4 8.0
GBP
|
61. 3
GBP
|
0. 9
GBP
|
— | — |
–
GBP
|
— | — |
0 .8
GBP
|
— | — | — | — |
–
GBP
|
–
GBP
|
— |
–
GBP
|
0 .1
GBP
|
–
GBP
|
0. 8
GBP
|
— | — | — | — | — | — | — | — | — |
| Dividends recognised as distributions to owners |
–
GBP
|
— | — | — |
–
GBP
|
–
GBP
|
4 9.0
GBP
|
— |
–
GBP
|
–
GBP
|
— | — |
–
GBP
|
— | — | — |
4 9.0
GBP
|
49 .0
GBP
|
2 5 .1
GBP
|
— | — |
–
GBP
|
— | — |
2 5 .1
GBP
|
— | — | — | — |
–
GBP
|
–
GBP
|
— |
–
GBP
|
–
GBP
|
–
GBP
|
2 5 .1
GBP
|
— | — | — | — | — | — | — | — | — |
| Increase (decrease) through share-based payment transactions, equity |
–
GBP
|
— | — | — |
–
GBP
|
4 .7
GBP
|
4,700,000
GBP
|
— |
–
GBP
|
–
GBP
|
— | — |
–
GBP
|
— | — | — |
4,700,000
GBP
|
–
GBP
|
0. 4
GBP
|
— | — |
–
GBP
|
— | — |
–
GBP
|
— | — | — | — |
0 .4
GBP
|
–
GBP
|
— |
–
GBP
|
–
GBP
|
–
GBP
|
0 .4
GBP
|
— | — | — | — | — | — | — | — | — |