Statement Of Changes In Equity [Abstract]
| Concept |
2023-01-01 to 2023-12-31 |
2023-01-01 to 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
2023-01-01 to 2023-12-31 |
2023-01-01 to 2023-12-31 |
As at 2023-12-31 |
2023-01-01 to 2023-12-31 |
As at 2023-12-31 |
As at 2023-12-31 |
2023-01-01 to 2023-12-31 |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
2022-01-01 to 2022-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Statement of changes in equity [abstract] | ||||||||||||||||||||||||||||||
| Statement of changes in equity [line items] | ||||||||||||||||||||||||||||||
| Equity | — | — |
415,300,000
GBP
|
1,423,900,000
GBP
|
369 .1
GBP
|
— | — |
479 .4
GBP
|
— |
167 .1
GBP
|
7 .0
GBP
|
— |
416,700,000
GBP
|
— | — |
1,482,200,000
GBP
|
— | — | — |
479 .4
GBP
|
430,100,000
GBP
|
167 .1
GBP
|
11,100,000
GBP
|
— |
460,500,000
GBP
|
1,499 .9
GBP
|
15,600,000
GBP
|
413,500,000
GBP
|
474,900,000
GBP
|
166,600,000
GBP
|
| Changes in equity [abstract] | ||||||||||||||||||||||||||||||
| Comprehensive income [abstract] | ||||||||||||||||||||||||||||||
| Profit (loss) |
27 .3
GBP
|
—
GBP
|
— | — | — |
27 .3
GBP
|
—
GBP
|
— |
—
GBP
|
— | — |
—
GBP
|
— |
—
GBP
|
—
GBP
|
— |
56,300,000
GBP
|
56,300,000
GBP
|
—
GBP
|
— | — | — | — |
—
GBP
|
— | — | — | — | — | — |
| Other comprehensive income |
3,800,000
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
7. 7
GBP
|
— | — | — | — | — | — | — | — | — | — | — | — | — |
| Comprehensive income |
31,100,000
GBP
|
1,400,000
GBP
|
— | — | — |
28,400,000
GBP
|
—
GBP
|
— |
—
GBP
|
— | — |
4,100,000
GBP
|
— |
3,200,000
GBP
|
—
GBP
|
— |
64,000,000
GBP
|
56,300,000
GBP
|
4,500,000
GBP
|
— | — | — | — |
—
GBP
|
— | — | — | — | — | — |
| Dividends recognised as distributions to owners |
89 .5
GBP
|
—
GBP
|
— | — | — |
89 .5
GBP
|
—
GBP
|
— |
—
GBP
|
— | — |
—
GBP
|
— |
—
GBP
|
—
GBP
|
— |
81,600,000
GBP
|
81,600,000
GBP
|
—
GBP
|
— | — | — | — |
—
GBP
|
— | — | — | — | — | — |
| Increase (decrease) through share-based payment transactions, equity |
100,000
GBP
|
—
GBP
|
— | — | — |
100,000
GBP
|
—
GBP
|
— |
—
GBP
|
— | — |
—
GBP
|
— |
—
GBP
|
—
GBP
|
— |
—
GBP
|
—
GBP
|
—
GBP
|
— | — | — | — |
—
GBP
|
— | — | — | — | — | — |