Disclosure Of Interests In Other Entities [Text Block]
| Concept | 
                                    
                                        As at 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  | 
                            
                                
                                    
                                        2022-01-01 to 2022-12-31  | 
                            
                                
                                    
                                        2022-01-01 to 2022-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        2021-01-01 to 2021-12-31  | 
                            
                                
                                    
                                        As at 2020-12-31  | 
                            
                        
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Disclosure of interests in other entities [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of interests in subsidiaries [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of subsidiaries [text block] | — | — | — | 
                                        
                                             
                                                17. Investment in subsidiaries – Group
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of subsidiaries [abstract] | |||||||||||||||
| Disclosure of subsidiaries [line items] | |||||||||||||||
| Current assets | 
                                        
                                             
                                                109,281,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
                                        
                                             
                                                227,728,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | 
| Non-current assets | 
                                        
                                             
                                                114,688,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
                                        
                                             
                                                113,410,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | 
| Current liabilities | 
                                        
                                             
                                                315,820,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
                                        
                                             
                                                46,147,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | 
| Non-current liabilities | 
                                        
                                             
                                                5,695,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
                                        
                                             
                                                336,178,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | 
| Revenue | — | — | — | 
                                        
                                             
                                                98,337,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | — | 
                                        
                                             
                                                131,387,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Profit (loss) | — | — | — | 
                                        
                                             
                                                56,359,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | — | 
                                        
                                             
                                                29,685,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Comprehensive income | — | 
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                56,359,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                56,359,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                -
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                -
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                29,685,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                29,685,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | 
| Disclosure of interests in associates [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of associates [text block] | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 
| Disclosure of associates [abstract] | |||||||||||||||
| Disclosure of associates [line items] | |||||||||||||||
| 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 | 
                                        
                                             
                                                32,783,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | 
                                        
                                             
                                                114,577,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | 
                                        
                                             
                                                77,956,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Tax expense (income) | — | — | — | 
                                        
                                             
                                                -
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — | — | — | — | — | — | — | 
                                        
                                             
                                                75,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    — | — |