A view of the river Foyle, from Grianan hill fort, which defines part of the Irish border. Counties Londonderry and Tyrone in Northern Ireland are to the left of the river, and County Donegal in the Republic lies to the right. Photo: William Kelly

Crossing the border between Northern Ireland and the south, it’s sometimes difficult to tell when you leave the kingdom and enter the Republic. The traffic signs are different and there are subtle clues too in the changing colour of road markings and even the texture of the asphalt. Your mobile phone will slip in and out of networks for several miles. The feeling is of one country fading indistinguishably into another. All around, there are signs of the activities that thrive in liminal places; petrol stations and shops taking advantage of the differences in tax and exchange rates, skid marks on the roads from jurisdiction-escaping joyriders, a hand-painted advertisement offering illegal “Red Diesel for Sale” discarded in a ditch.

Tied to a lamppost, near a defunct custom post, is a placard titled, “Respect the Remain Vote.” It continues, “Warning! If there is a hard border this road may be closed from March 2019.” It is signed, “Border Communities Against Brexit.” All along the 310-mile border between Northern Ireland and the Republic, such signs remind travellers and locals that the boundary will likely not remain invisible for long.

Ireland, north and south, is facing a border crisis. What is now a boundary between two European Union countries will soon be the Brexit frontline between the EU and the United Kingdom. When he visited the north in August, the new and decidedly worried Irish Taoiseach, Leo Varadkar, took a stark tone when he addressed a crowd a…

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