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Financial Instruments Risk Management - Additional Information (Details) - GBP (£)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Financial Instruments [Line Items]        
Cash and cash equivalents £ 87,356,000 £ 51,962,000 £ 76,972,000 £ 86,703,000
Interest Rate Risk [member]        
Disclosure Of Financial Instruments [Line Items]        
Cash and cash equivalents £ 87,400,000 52,000,000    
Increase in interest rates 0.50%      
Increase in interest income on cash and cash equivalents held on variable and short term fixed rate deposits £ 269,511 244,674    
Currency Risk [member]        
Disclosure Of Financial Instruments [Line Items]        
Cash and cash equivalents £ 70,419,000 28,980,000    
Percentage of increase in foreign exchange rate 1.00%      
Reduction in financial assets and liabilities in foreign currencies £ (710,592) £ (295,498)