Taoiseach Leo Varadkar has used the story of an IRA bombing of a customs post to emphasise the importance of the border issue to EU leaders.
Mr Varadkar brought in a copy of an Irish newspaper to the summit dinner last night which featured the story of the IRA blast which killed nine people in August 1972.
Four customs officials, two lorry drivers and three IRA men died in the explosion at Newry customs clearing station.
Mr Varadkar held up a copy of yesterday's Irish Times during the meeting to stress the importance of how far Northern Ireland and Ireland have come since the Troubles, journeying from violence to peace.
The family of one of the lorry drivers said they fear Brexit could spark renewed violence along the border.
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Jack McCann, from Co Monaghan, died in the explosion which was the worst attack on a Northern Ireland customs post during the Troubles.
Mr McCann's daughter Mary Casey, who was 21 when her father died, spoke of her fear of border custom posts returning in the wake of a no-deal Brexit.
She told the newspaper that she believes there will be a hard border.
"I don't know how else it is going to work, to be honest. It would be scary. I imagine it is going back to the way it was."
She made the comments ahead of a two-day European Council summit in Brussels where EU leaders are discussing the Irish border issue.
Four customs officials were killed when the bomb exploded prematurely, including Frank Quinn, Patrick Murphy, Michael Ronan Gilleece and Marshall Lawrence.
The three IRA members - Noel Madden, Patrick Hughes and Oliver Rowntree, all from Newry - were also killed.
The two lorry drivers who were killed were waiting for customs clearance when the IRA men entered the building and ordered everyone to leave.
Mrs Casey spoke of how young people may react to a hard border and Brexit.
"An awful lot of people around here wouldn't know," she told the Irish Times.
"You see if Brexit brings the violence back, they will be younger and they will have no fear because they won't remember."
Mr Quinn's brother Artie also spoke of his fears of the possible Brexit outcome.
"I would have concerns that the symbolism of check points, queues and lorries having to wait to get checked out - the symbolism of division and disruption - that would not be desirable," he said.
"It would bring back memories of a time before, when there was that visible division, and nobody wants to see that again.
"If you take a straw poll around Newry, no-one wants to see a return to that kind of violence no matter how romanticised it may be in the eyes of some. Only a minority would go to those lengths."
