evidence: One of the most difficult issues in the entire Brexit process is how to ensure that there is no return to a hard border between Northern Ireland and the Irish Republic, once that border becomes the external border of the European Union, of its single market and its customs union. [...] An open border is a vital part of the 1998 Good Friday Agreement which underpins the Northern Ireland peace process. [...] But drivers hoping to cross the border say they often have to wait for more than 24 hours at busy times.