Disclosure Of Leases [Text Block]
| Concept | 
                                    
                                        2022-01-01 to 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                        
|---|---|---|---|
| Disclosure of leases [text block] | 
                                        
                                             
                                                25. Lease liability – Group
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Presentation of leases for lessee [abstract] | |||
| Right-of-use assets | — | 
                                        
                                             
                                                6,834,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                7,877,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Lease liabilities [abstract] | |||
| Current lease liabilities | — | 
                                        
                                             
                                                1,765,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                2,129,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Non-current lease liabilities | — | 
                                        
                                             
                                                5,695,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                7,416,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Disclosure of quantitative information about leases for lessee [abstract] | |||
| Disclosure of quantitative information about right-of-use assets [text block] | 
                                        
                                             
                                                16. Right-of-use (‘ROU’) asset – Group
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Disclosure of quantitative information about right-of-use assets [abstract] | |||
| Disclosure of quantitative information about right-of-use assets [line items] | |||
| Reconciliation of changes in right-of-use assets [abstract] |