Answer
The answer is the third congress of the Communist International (Comintern), held in Moscow from June 22 to July 12, 1921. Hewlett was one of the delegates representing the Communist Party of Great Britain. The congress was significant for adopting the "Twenty-One Conditions", which set out the terms for communist parties to join the Comintern and emphasized the importance of democratic centralism and strict adherence to the Comintern's line.