Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept |
As at 2023-12-31 |
As at 2023-12-31 |
As at 2022-12-31 |
As at 2022-12-31 |
As at 2021-12-31 |
As at 2021-12-31 |
|---|---|---|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | ||||||
| Property, plant and equipment [abstract] | ||||||
| Property, plant and equipment |
49,900,000
GBP
|
19,100,000
GBP
|
54,300,000
GBP
|
21,000,000
GBP
|
— | — |
| Investment property [abstract] | ||||||
| Investment property |
4,551,400,000
GBP
|
–
GBP
|
5,002,000,000
GBP
|
–
GBP
|
— | — |
| Investments in subsidiaries, joint ventures and associates reported in separate financial statements [abstract] | ||||||
| Investments in subsidiaries reported in separate financial statements | — |
2,189,800,000
GBP
|
— |
2,224,700,000
GBP
|
— | — |
| Investments accounted for using equity method [abstract] | ||||||
| Investments in joint ventures accounted for using equity method |
35,800,000
GBP
|
— |
43,900,000
GBP
|
— | — | — |
| Trade and other non-current receivables [abstract] | ||||||
| Other non-current receivables |
201,000,000
GBP
|
–
GBP
|
188,100,000
GBP
|
–
GBP
|
— | — |
| Miscellaneous non-current assets [abstract] | ||||||
| Non-current net defined benefit asset |
2,000,000
GBP
|
2,000,000
GBP
|
1,200,000
GBP
|
1,200,000
GBP
|
— | — |
| Non-current derivative financial assets |
2,900,000
GBP
|
2,900,000
GBP
|
5,000,000
GBP
|
5,000,000
GBP
|
— | — |
| Trade and other current receivables [abstract] | ||||||
| Trade and other current receivables |
42,700,000
GBP
|
2,359,100,000
GBP
|
42,400,000
GBP
|
1,788,000,000
GBP
|
— | — |
| Cash and cash equivalents [abstract] | ||||||
| Cash and cash equivalents |
73,000,000
GBP
|
24,800,000
GBP
|
76,600,000
GBP
|
67,300,000
GBP
|
105,500,000
GBP
|
90,600,000
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
|
54,200,000
GBP
|
–
GBP
|
— | — |
| Classes of other provisions [abstract] | ||||||
| Other provisions [abstract] | ||||||
| Other non-current provisions |
300,000
GBP
|
300,000
GBP
|
200,000
GBP
|
200,000
GBP
|
— | — |
| Other current provisions |
100,000
GBP
|
100,000
GBP
|
–
GBP
|
–
GBP
|
— | — |
| Borrowings [abstract] | ||||||
| Non-current portion of non-current borrowings |
1,233,200,000
GBP
|
1,053,600,000
GBP
|
1,229,400,000
GBP
|
1,048,400,000
GBP
|
— | — |
| Current borrowings and current portion of non-current borrowings [abstract] | ||||||
| Current borrowings |
102,900,000
GBP
|
82,900,000
GBP
|
19,700,000
GBP
|
–
GBP
|
— | — |
| Non-current portion of non-current borrowings, by type [abstract] | ||||||
| Trade and other current payables [abstract] | ||||||
| Trade and other current payables |
148,000,000
GBP
|
2,009,600,000
GBP
|
148,100,000
GBP
|
1,707,500,000
GBP
|
— | — |
| Issued capital [abstract] | ||||||
| Issued capital |
5,600,000
GBP
|
5,600,000
GBP
|
5,600,000
GBP
|
5,600,000
GBP
|
— | — |
| Retained earnings [abstract] | ||||||
| Retained earnings |
2,367,300,000
GBP
|
304,100,000
GBP
|
2,931,400,000
GBP
|
202,200,000
GBP
|
— | — |
| Net assets (liabilities) [abstract] | ||||||
| Assets |
5,028,000,000
GBP
|
4,600,600,000
GBP
|
5,509,400,000
GBP
|
4,110,200,000
GBP
|
— | — |
| Liabilities |
1,519,200,000
GBP
|
3,168,100,000
GBP
|
1,433,900,000
GBP
|
2,779,900,000
GBP
|
— | — |
| Assets (liabilities) |
3,508,800,000
GBP
|
1,432,500,000
GBP
|
4,075,500,000
GBP
|
1,330,300,000
GBP
|
— | — |
| Net current assets (liabilities) [abstract] | ||||||
| Current assets |
185,000,000
GBP
|
2,384,200,000
GBP
|
160,700,000
GBP
|
1,855,300,000
GBP
|
— | — |
| Current liabilities |
251,400,000
GBP
|
2,093,900,000
GBP
|
169,200,000
GBP
|
1,709,700,000
GBP
|
— | — |
| Assets less current liabilities [abstract] |