Could Northern Ireland soon face a huge decision - whether to leave the UK? Andrea Catherwood returns to where she grew up to discover why the biggest question of all is looming beyond Brexit. Demography may soon leave Catholics as the largest population group. And Brexit debate over new border controls in Ireland has challenged the uneasy compromise of the Good Friday Agreement. So how could a vote on creating a united Ireland come about? How would different traditions and generations decide what to do? And away from political debate, how do the people of Northern Ireland feel about the prospect of such a sensitive and fundamental choice?