The centenary of Northern Ireland is prompting reflections on the past, evaluations of the present and predictions about the future.
Demographic change, recent elections and Brexit have all fuelled an increased debate about the potential for constitutional change.
In a series of reports for PM on BBC Radio 4, I’ve been looking at the state of the union in Northern Ireland.
What does the Good Friday Agreement say?
The deal says Northern Ireland will remain in the union as long as most of its people wanted it to be.
But it includes a potential future pathway to a united Ireland through a referendum, also called a border poll.
The text which in UK law says the Northern Ireland secretary “shall exercise the power [to call a referendum] if at any time it appears likely… that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom”.