Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2023-12-31 |
As at 2022-12-31 |
As at 2022-01-01 |
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Property, plant and equipment [abstract] | |||
| Property, plant and equipment |
22,000,000.000000
GBP
|
22,000,000.000000
GBP
|
14,000,000.000000
GBP
|
| Intangible assets and goodwill [abstract] | |||
| Intangible assets and goodwill |
41,000,000.000000
GBP
|
47,000,000.000000
GBP
|
45,000,000.000000
GBP
|
| Investment property [abstract] | |||
| Investment property |
32,000,000.000000
GBP
|
40,000,000.000000
GBP
|
70,000,000.000000
GBP
|
| Investments accounted for using equity method [abstract] | |||
| Investments accounted for using equity method |
149,000,000.000000
GBP
|
194,000,000.000000
GBP
|
–
GBP
|
| Trade and other receivables [abstract] | |||
| Trade and other receivables |
60,000,000.000000
GBP
|
33,000,000.000000
GBP
|
21,000,000.000000
GBP
|
| Prepayments and accrued income including contract assets [abstract] | |||
| Prepayments and accrued income including contract assets |
12,000,000.000000
GBP
|
11,000,000.000000
GBP
|
6,000,000.000000
GBP
|
| Cash and cash equivalents [abstract] | |||
| Cash [abstract] | |||
| Cash |
546,000,000.000000
GBP
|
482,000,000.000000
GBP
|
510,000,000.000000
GBP
|
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract] | |||
| Non-current assets or disposal groups classified as held for sale |
–
GBP
|
–
GBP
|
3,000,000.000000
GBP
|
| Classes of other provisions [abstract] | |||
| Other provisions [abstract] | |||
| Other provisions |
3,000,000.000000
GBP
|
1,000,000.000000
GBP
|
1,000,000.000000
GBP
|
| Borrowings [abstract] | |||
| Borrowings |
686,000,000.000000
GBP
|
699,000,000.000000
GBP
|
774,000,000.000000
GBP
|
| Borrowings, by type [abstract] | |||
| Trade and other payables [abstract] | |||
| Accruals and deferred income including contract liabilities [abstract] | |||
| Accruals and deferred income including contract liabilities |
47,000,000.000000
GBP
|
43,000,000.000000
GBP
|
43,000,000.000000
GBP
|
| Trade and other payables |
20,000,000.000000
GBP
|
96,000,000.000000
GBP
|
81,000,000.000000
GBP
|
| Miscellaneous liabilities [abstract] | |||
| Investment contracts liabilities |
35,000,000.000000
GBP
|
33,000,000.000000
GBP
|
34,000,000.000000
GBP
|
| Issued capital [abstract] | |||
| Issued capital |
104,000,000.000000
GBP
|
104,000,000.000000
GBP
|
104,000,000.000000
GBP
|
| Retained earnings [abstract] | |||
| Retained earnings |
259,000,000.000000
GBP
|
354,000,000.000000
GBP
|
33,000,000.000000
GBP
|
| Accumulated other comprehensive income [abstract] | |||
| Reserve of exchange differences on translation |
1,000,000.000000
GBP
|
1,000,000.000000
GBP
|
— |
| Net assets (liabilities) [abstract] | |||
| Assets |
31,838,000,000.000000
GBP
|
25,412,000,000.000000
GBP
|
26,401,000,000.000000
GBP
|
| Liabilities |
30,635,000,000.000000
GBP
|
24,309,000,000.000000
GBP
|
24,905,000,000.000000
GBP
|
| Assets less current liabilities [abstract] |