The use of referendums as a way to complement representative democracy can pose fundamental risks to the democratic system of decision making, where the question on ballot paper lacks clarity either due to the complexity of the issue to be decided, or to poor phrasing. Another set of risks relate to the challenges of ensuring high standards of veracity, transparency and accountability in an era where illicit use of digital technology might influence voters. Potential partisan capture of the process is yet another example of a systemic threat to manipulate the vote. These types of risks came into sharp focus during and in the aftermath of the UK ‘Brexit’ poll on the 23 June 2016. I use this unique case study to discuss a selection of issues that emerged from the referendum vote under the UK’s uncodified constitution, and to evaluate the place of referenda in political decision-making in constitutional democracies more generally.