Statement Of Changes In Equity [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 |
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 changes in equity [abstract] | ||||||||||
| Statement of changes in equity [line items] | ||||||||||
| Dividends recognised as distributions to owners of parent |
–
GBP
|
–
GBP
|
–
GBP
|
32,300,000
GBP
|
32,300,000
GBP
|
9,600,000
GBP
|
–
GBP
|
9,600,000
GBP
|
–
GBP
|
–
GBP
|
| Increase (decrease) through exercise of options, equity |
–
GBP
|
–
GBP
|
–
GBP
|
1,700,000
GBP
|
1,700,000
GBP
|
900,000
GBP
|
–
GBP
|
900,000
GBP
|
–
GBP
|
–
GBP
|
| Decrease (increase) through tax on share-based payment transactions, equity |
–
GBP
|
–
GBP
|
–
GBP
|
8,200,000
GBP
|
8,200,000
GBP
|
800,000
GBP
|
–
GBP
|
800,000
GBP
|
–
GBP
|
–
GBP
|
| Purchase of treasury shares |
–
GBP
|
–
GBP
|
–
GBP
|
33,600,000
GBP
|
33,600,000
GBP
|
9,600,000
GBP
|
–
GBP
|
9,600,000
GBP
|
–
GBP
|
–
GBP
|