This article looks at the continued calls for popular participation in UK constitution-making following the 2014 Scottish independence and 2016 Brexit referendums. In particular, it discusses the prospect of a UK constitutional convention being set up to deliberate upon and make recommendations concerning constitutional reform. The article proceeds by first mapping the arguments in favour of setting up such a body in a country with little but growing experience with direct democracy. It then analyses three difficulties surrounding a UK constitutional convention: deciding on a manageable mandate, identifying the political community or communities it is to represent and the method for selecting its membership, and defining the place of such a convention within the UK’s broader constitution-making mechanisms. The article highlights fundamental unknowns in need of clarification before such an instrument could be used while at the same time admitting the limitations of a constitutional convention as a panacea for all of the UK’s constitutional woes. In exploring these questions, the article shows how constitutional reform debates in the UK are no less complex than were those surrounding Scottish independence and have been further compounded by Brexit.