AbstractThis article employs the image of the antisyzygy, the yoking of opposites, as an analytical tool to understand the dynamic and unresolved tensions built into the very idea of the European Union. It describes the EU as a forming a supranational constitutional space which does not supersede nation states, but instead seeks to preserve their specific identities while promoting and protecting the fundamental values they are called upon to embody as liberal constitutional democracies. The article then critically examines constitutional developments in the UK subsequent to its decision to leave the European Union and suggests that, paradoxically, it may have been the European Union which held the post‐War post‐imperial United Kingdom together and, without it and outside it, we may anticipate the UK's imminent dissolution into its original constituent nations – Brexit leads inexorably to BreUK‐up.