In this pamphlet, Prof. Bogdanor assesses the potential impact of Brexit upon the ‘unwritten’ UK constitution. He notes that it is rare if not unprecedented for a democracy to exit from a major international human rights regime; and that no country has hitherto moved from a protected to an unprotected system. Such a process, he concludes, raises profound constitutional questions. Brexit will leave a gap in our constitution in terms of the protection of human rights. This gap could well be filled by the judges. If that happens, Brexit will increase the danger of a clash between judges and Parliament. In addition, Brexit might prove to be a constitutional moment for Britain, since it may strengthen the case for Britain following nearly every other democracy in developing a codified constitution which provides for the judicial protection of human rights. Our entry into the EU transformed the British constitution. Brexit, far from returning us to the status quo ante, could transform it even more.