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Cash and Cash Equivalents - Schedule of Detailed Information About Cash and Cash Equivalents (Detail) - GBP (£)
£ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Cash And Cash Equivalents [Abstract]        
Cash and cash equivalents £ 87,356 £ 51,962 £ 76,972 £ 86,703