There is a magical thing in Ireland called the Common Travel Area arrangement that allows the free movement of people between Northern Ireland and the Republic of Ireland. However the shadow of Brexit is now threatening this. Before becoming Prime Minister, Theresa M ay said that she believed there would have to be a hard border between the north and the south.
Politicians on both sides of the political divide in Ireland are worried because they don't see how the CTA could survive a re-instatement of the border.
More worryingly they think this would undermine at lot of the work that has been done to ensure the stability of the Irish peace process since the Troubles in the 60s, 70S and 80s.. As someone who grew up in this period this is a very frightening prospect. Ireland is at peace now, but it wasn't that long ago that killings and atrocities were common place. People tend to forget that this happened on British soil, but it did.
We can not let it re-start.