Disclosure Of Interests In Other Entities [Text Block]
| Concept | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | As at 2024-12-31 | 2024-01-01 to 2024-12-31 | 2024-01-01 to 2024-12-31 | 2023-01-01 to 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 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 2023-01-01 to 2023-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Disclosure of interests in other entities [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of interests in subsidiaries [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of subsidiaries [text block] | — |  | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of subsidiaries [abstract] | ||||||||||||||||
| Disclosure of subsidiaries [line items] | ||||||||||||||||
| Current assets | — | — | — | — | — | 
                                                188,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                159 .8
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Non-current assets | — | — | — | — | — | 
                                                157 .6
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                279 .2
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Current liabilities | — | — | — | — | — | 
                                                118,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                65,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Non-current liabilities | — | — | — | — | — | 
                                                141,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                143,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Revenue | — | 
                                                283,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                306. 9
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
| Profit (loss) | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                147 .0
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                147 .0
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                78. 1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                78. 1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Comprehensive income | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                153,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                2 .5
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                3,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                147 .3
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                91,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                1,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                78,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                12 .2
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Disclosure of interests in associates [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of associates [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of associates [abstract] | ||||||||||||||||
| Disclosure of associates [line items] | ||||||||||||||||
| Profit (loss) from continuing operations | — | 
                                                147 .0
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                12. 1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
| Profit (loss) from discontinued operations | — | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                66,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
| Other comprehensive income | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                2 .5
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                3,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                13. 1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
                                                1,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                0 .1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                12,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Disclosure of interests in joint arrangements [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of joint ventures [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of joint ventures [abstract] | ||||||||||||||||
| Disclosure of joint ventures [line items] | ||||||||||||||||
| Cash and cash equivalents | — | — | — | — | — | 
                                                57 .3
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                8. 7
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Tax expense (income) | — | 
                                                43,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | — | 
                                                6,700,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — |