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General Information- Additional Information (Detail)
12 Months Ended
Dec. 31, 2020
Subsidiary
Disclosure Of General Information About Financial Statements [Abstract]  
Name of reporting entity NuCana plc
Description of nature of entity's operations clinical-stage biopharmaceutical company developing a portfolio of new medicines to treat patients with cancer
Domicile of entity United Kingdom
Country of incorporation England and Wales
Name of subsidiary NuCana, Inc. and NuCana BioMed Trustee Company Limited
Number of subsidiaries 2