Establishment of Official Opposition a momentous change
The passing of an Opposition Bill by an independent Assembly member who has since lost his seat has paved the way for one of the most momentous changes since political powersharing was established in 1998.
For years, Ulster Unionist leader David Trimble and his successors wrestled with the dilemma of sharing power in a mandatory coalition with a Sinn Fein which retained links with an IRA with its arms intact.
The issue helped prompt repeated crises in the devolved administration and so badly split the UUP that it conceded unionist primacy to the Democratic Unionists.
Now the UUP has finally left the big tent it helped create in a stated return to "normal democracy" after years of effective opposition from across the ministerial Executive table.
Leader Mike Nesbitt said: "Given the evidence that little is about to change, and we face another five years of DUP/Sinn Fein carve up and mutual veto, we are convinced the right thing to do for the country is to forego our entitlements in government and establish an Official Opposition, to both scrutinise the work of the next Executive and offer the electorate something different next time around."
The role of Leader of the Opposition is certain to go to Mr Nesbitt, as representative of the largest party. The government's opponents will also be entitled to chair the powerful financial scrutiny body the Public Accounts Committee (PAC).
There will be Opposition Day Debates on topics likely to hurt the governing administration. Extra research funding and services will be used to critique government policy. And there will be additional speaking rights.
Only parties large enough to take an Executive seat will be entitled to the recognition, the Ulster Unionists and Social Democratic and Labour Party (SDLP).
The SDLP has yet to make its position on official opposition known.
John McCallister, a former Ulster Unionist who left for a short-lived rival party and latterly sat in the Assembly as an independent, lost his seat during this month's poll.
His last substantive work was to secure the backing of Assembly members for his Private Members Bill paving the way for the creation of an official opposition.
The Bill was backed by Assembly members but opposed by Sinn Fein as a "Frankenstein's Monster" that could not be controlled.
This will be the first official opposition at Stormont since 1972 when power was taken over by direct rule ministers from London.
Mandatory coalition rules were introduced in 1998 to enshrine the protection of minority voices in a society emerging from conflict.
For decades since its inception Northern Ireland's government was dominated by one party, the Official Unionists, and the measure helped assuage nationalist fears of renewed hegemony.
The Ulster Unionists resigned their Regional Development post in the Executive last year after a row about a killing by IRA members. They will not be returning.