Twenty years after the signing of The Good Friday Agreement that brought peace to Northern Ireland, Brexit has unleashed new uncertainty about the island's future. In 2016 the UK voted to leave the European Union but Northern Ireland voted to remain. Irish nationalists in the north are unhappy about the possibility that controls on the land border with the Republic of Ireland could return. Supporters of a united Ireland have seized on this to argue that by joining the Republic, Northern Ireland would be able to get back into the EU. The Good Friday Agreement includes a provision for a referendum on unification known as a border poll. Whether nationalists could win is unclear but a mixture of worries about Brexit and demographic change suggest a future border poll would be much tighter than would have been the case ten years ago. Ritula Shah and a panel of experts discuss whether Brexit has opened the door to a united Ireland. (Photo: Farmer standing on the border separating Northern Ireland and the Republic of Ireland. Credit: Charles McQuillan/Getty Images)