Disclosure Of Revenue From Contracts With Customers [Text Block]
| Concept | 
                                    
                                        2022-01-01 to 2022-12-31  | 
                            
                                
                                    
                                        As at 2022-12-31  | 
                            
                                
                                    
                                        As at 2021-12-31  | 
                            
                        
|---|---|---|---|
| Disclosure of revenue from contracts with customers [text block] | 
                                        
                                             
                                                18. Amounts receivable from customers – Group
                                                
                                             
                                        
                                     | 
                                
                                    — | — | 
| Receivables from contracts with customers [abstract] | |||
| Non-current receivables from contracts with customers | — | 
                                        
                                             
                                                101,969,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                98,836,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                            
| Current receivables from contracts with customers | — | 
                                        
                                             
                                                75,135,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     | 
                                
                                    
                                        
                                             
                                                109,148,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             
                                        
                                     |