In a Thursday speech to the Brookings Institution in DC, Varadkar said "there can be no upside" to Brexit, but that Ireland must respect it.

Unfortunately, a likely outcome of Brexit will be a customs frontier between Ireland and Northern Ireland, which could adversely impact the power-sharing government of the Island of Ireland and lead to a breakdown of the Good Friday Agreement.

Theresa May's UK government - which needs the support on the NI DUP to remain in power - needs to work harder, and faster, on resolving this issue.