Statement Of Comprehensive Income [Abstract]
| Concept |
2023-01-01 to 2023-12-31 |
2023-01-01 to 2023-12-31 |
2023-01-01 to 2023-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
2022-01-01 to 2022-12-31 |
|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||
| Profit (loss) |
223,400,000
GBP
|
223,400,000
GBP
|
223,400,000
GBP
|
204,300,000
GBP
|
204,300,000
GBP
|
204,300,000
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) on remeasurements of defined benefit plans |
2,400,000
GBP
|
— | — | — |
16,300,000
GBP
|
— |
| Income tax relating to components of other comprehensive income that will not be reclassified to profit or loss [abstract] | ||||||
| Income tax relating to remeasurements of defined benefit plans included in other comprehensive income |
700,000
GBP
|
— | — | — |
2,400,000
GBP
|
— |
| Other comprehensive income |
1,700,000
GBP
|
1,700,000
GBP
|
1,700,000
GBP
|
13,900,000
GBP
|
13,900,000
GBP
|
13,900,000
GBP
|
| Comprehensive income |
221,700,000
GBP
|
221,700,000
GBP
|
221,700,000
GBP
|
190,400,000
GBP
|
190,400,000
GBP
|
190,400,000
GBP
|