Former Irish president Mary McAleese has said border controls and identity checks between Northern Ireland and the Republic are "inevitable" after the UK leaves the EU.
n an interview with RTE she said that given the importance the British government gave to controlling immigration, border controls would have to be put in place.
The north Belfast woman said it would "break her heart" to have to produce identification every time she crossed the border.
She described the Brexit process as "pulling a tooth with 10,000 roots" and that she was worried about the future of power-sharing in Belfast.
"We need to start hearing how it will be alright," she said.
The prospect of a united Ireland, she said, had been brought to the fore by Brexit and there was a need for "new language, new ideas and new understandings" in order to accommodate unionists.