Support for the Good Friday peace agreement has been withdrawn by a group representing the main loyalist paramilitary factions in Northern Ireland.
They say the creation of an EU customs border under the Brexit deal undermines the union with Great Britain.
The Good Friday Agreement brought to an end more than 30 years of conflict, which claimed more than 3,500 lives.
It comes amid a push for a referendum on Irish unity from the main nationalist party, Sinn Féin. In this special report, Fergal Keane has been testing reaction to that idea from diverse unionist voices.