Analysis Of Income And Expense [Abstract]
| 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 | 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 | 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 | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Analysis of income and expense [abstract] | ||||||||||||||
| Revenue [abstract] | ||||||||||||||
| Revenue | — | 
                                                283,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                306. 9
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Material income and expense [abstract] | ||||||||||||||
| Finance income (cost) | — | 
                                                6. 9
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                14. 1
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Operating expense excluding cost of sales | — | 
                                                191. 9
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                119 .3
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | 
| Comprehensive income, continuing and discontinued operations [abstract] | ||||||||||||||
| 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
                                                    
                                                
                                             | 
                                                78,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                12 .2
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Comprehensive income attributable to owners of parent, continuing and discontinued operations [abstract] | ||||||||||||||
| Comprehensive income, attributable to owners of parent | — | 
                                                153,300,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | — | — | 
                                                91,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — |