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 | 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 | 2022-01-01 to 2022-12-31 | 2022-01-01 to 2022-12-31 | 
|---|---|---|---|---|---|---|---|---|---|---|
| Statement of comprehensive income [abstract] | ||||||||||
| Profit (loss) | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                8,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                8,400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Other comprehensive income [abstract] | ||||||||||
| Components of other comprehensive income that will not be reclassified to profit or loss, net of tax [abstract] | ||||||||||
| Other comprehensive income, net of tax, gains (losses) on revaluation of property, plant and equipment, right-of-use assets and intangible assets | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Other comprehensive income that will not be reclassified to profit or loss, net of tax | — | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | — | — | — | 
                                                6,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | — | 
| Other comprehensive income | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,600,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,800,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Comprehensive income | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,100,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                6,500,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                400,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                15,000,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                15,200,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             |