evidence: The international border between Northern Ireland and the Republic of Ireland is about 310 miles long with, depending on how many tracks you include, as many as 275 crossing points. [...] The other concern of course is economic. The economies of Northern Ireland and the Republic are completely interconnected. Huge amounts of goods and services cross the border every day without checks of any kind. [...] It is also estimated that at least 30,000 people cross the border every day for work. The movement of people is governed by the Common Travel Area between the UK and Ireland, which predates the EU.