The American constitutional theorist Bruce Ackerman has recently suggested that the UK Parliament should call a constitutional convention to draft a written constitution that can be put to voters in a national referendum after a two-year drafting period. In this article, I examine a number of points of disjoint between these proposals and Ackerman’s own, “dualist” theory of constitutional change, developed from an intriguingly novel reading of American constitutional history. While this theory advocates generation-spanning, multi-institutional processes of constitutional change, Ackerman’s UK proposals involve a more fleeting and nationalistic approach, with unitary majorities apparently reigning supreme. The question is: can this disjoint between Ackerman 1 and Ackerman 2 be justified as Ackerman’s attempt to work within the contours of the UK’s constitutional culture, traditionally conceived? Or might Ackerman’s unfiltered American theory have something important to offer a UK audience today, given the divisions that the Brexit process has revealed in British society between opposing, traditional and non-traditional understandings of British sovereignty and democracy?