UNSPECIFIED, NORTHERN IRELAND - MAY 06: Kerbstones painted red, white and blue to signify unionist territory at a road junction near the Irish border in Fermanagh can be seen on May 6, 2016 in Northern Ireland. With many roads between the north and south of Ireland unmarked, visual clues such as kerbstones, flags and murals are the only representation that a border has been crossed. The United Kingdom has just one external land border which is located between Northern Ireland and the Republic of Ireland. At present there are no checkpoints in place for anyone crossing this border, either by foot or vehicle. Prior to the Anglo-Irish agreement anyone wishing to cross the border was subjected to armed checkpoints while unguarded country roads were blocked by concrete barricades. With the Brexit referendum taking place on June 23 to decide whether Britain should remain in the European Union some politicians have warned that the open border could be used as a possible backdoor entrance by migrants, traffickers and criminals wishing to gain access to the UK following a decision to leave the EU. (Photo by Charles McQuillan/Getty Images)
