evidence: The Border between the Republic of Ireland and Northern Ireland has been the issue that has bedevilled the Brexit negotiations, one that has overshadowed the departure of the United Kingdom from the European Union. [...] The crisis provoked by the need to ensure that the Border remains "open" in all circumstances has come as a surprise to many of those who voted in the referendum on June 23rd, 2016. [...] Brussels believed a hard border could be avoided and the Belfast Agreement upheld if Northern Ireland remained fully aligned with the European Union's customs union and part of the single market after Brexit.