Subclassifications Of Assets, Liabilities And Equities [Abstract]
| Concept | As at 2022-12-31 | As at 2021-12-31 | As at 2020-12-31 | 
|---|---|---|---|
| Subclassifications of assets, liabilities and equities [abstract] | |||
| Investment property [abstract] | |||
| Investment property | 
                                                71,160,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                87 ,565
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Trade and other current receivables [abstract] | |||
| Trade and other current receivables | 
                                                1,143,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                2,87 6
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Cash and cash equivalents [abstract] | |||
| Cash and cash equivalents | 
                                                7, 2 0 6
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                5,715,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                3, 295
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners [abstract] | |||
| Non-current assets or disposal groups classified as held for sale or as held for distribution to owners | 
                                                6, 750
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Borrowings [abstract] | |||
| Current borrowings and current portion of non-current borrowings [abstract] | |||
| Current borrowings | 
                                                –
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                7 ,500
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Non-current portion of non-current borrowings, by type [abstract] | |||
| Non-current portion of other non-current borrowings | 
                                                27 ,200
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                19, 700
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Trade and other current payables [abstract] | |||
| Trade and other current payables | 
                                                2, 883
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                2, 839
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Issued capital [abstract] | |||
| Issued capital | 
                                                1,299,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                1,296,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Retained earnings [abstract] | |||
| Retained earnings | 
                                                13,481,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                15,7 69
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Miscellaneous equity [abstract] | |||
| Reserve of share-based payments | 
                                                160,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                102,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Capital redemption reserve | 
                                                95,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                95,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Net assets (liabilities) [abstract] | |||
| Assets | 
                                                86,259,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                96,156,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Liabilities | 
                                                30,083,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                30,039,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Assets (liabilities) | 
                                                56,176,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                66,117,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Net current assets (liabilities) [abstract] | |||
| Current assets | 
                                                15,099,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                8,591,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Current liabilities | 
                                                2,883,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | 
                                                10,339,000
                                                
                                                    
                                                        GBP
                                                    
                                                
                                             | — | 
| Assets less current liabilities [abstract] |