The UK’s planned exit from the EU is a constitutionally momentous decision. Significant constitutional questions regarding the causes and consequences can be raised. One important aspect is the constant undercurrent of British constitutional dissatisfaction with supranational multilevel governance. Key questions are the following: First, why has EU multilevel governance been perceived as a threat to British constitutional identity? Second, why is the UK currently confronted with domestic confusion over the constitutionally appropriate procedures for Brexit? Third, whether the UK eventually leaves the EU or not, has the time come for the UK to adopt a codified constitution? Faced with uncertainty over the UK’s future international standing, it may become imperative for the UK to operate within systems of multilevel governance, and relevant constitutional hurdles have to be addressed.