For the British government, the Biden visit to Belfast posed one major exam question: would the pageantry of a pan-nationalist juggernaut rolling into town, led by the most tribally Irish-American President of all time, make it appreciably harder for the DUP to accept the Windsor Framework and so to re-establish the Stormont Executive as the cornerstone of the Good Friday Agreement? For as it stands, Rishi Sunak’s mission to stabilise the Union in all its constituent parts is not yet complete.