"For more than 80 years, since the war of independence, successive Irish governments have wanted the IRA to go away. Eamon de Valera, in the 1930s worried about the guns still in their hands. In 1938, in a dreadful act of irresponsibility, surviving members of the Second Dáil, then no longer in Leinster House, abdicated such political legitimacy as they possessed to the IRA," he says.

While not expecting DUP leader Ian Paisley to accept such a "radical step" as enough, Mansergh believes "it is best to let the new reality, in which the IRA has, in an astonishing reversal from 1938, handed back the baton to Sinn Féin, gradually sink in".