The DUP has played a central role in the latest act of the Brexit drama.
Downing Street’s concerted efforts to win over the party has highlighted just how much influence the unionists have wielded in the process.
So how did a party whose 10 MPs secured fewer votes in the last general election than the population of Milton Keynes land its leading part?
– 2016 EU referendum:
The party’s support for Brexit was not a foregone conclusion in 2016.
The referendum campaign did not divide neatly along traditional orange/green lines in Northern Ireland.
While the DUP undoubtedly counted committed Brexiteers within its ranks, there were other senior members who had a more pro-European outlook, some of whom were rumoured to have voted Remain.
With the party styling itself as pro-business and having a strong farming support base, it would not have been a major surprise if the DUP had opted to sit on the fence, allowing its representatives to take their own position on the divisive issue.
When the party did declare for Brexit, it campaigned for it enthusiastically.
At one point, it shelled out hundreds of thousands of pounds for a full wraparound advert in the Metro newspaper.
That incident sparked controversy in Northern Ireland when it emerged that the party paid for the ad – in a paper not printed in Northern Ireland – with part of a £400,000-plus donation from a little known Brexit-backing group called the Constitutional Research Council.
– 2017 general election:
The snap election catapulted the DUP into the unexpected role of parliamentary kingmakers when Theresa May lost her majority.
The then prime minister was only able to form a workable government through a confidence and supply arrangement with the party’s 10 MPs.
In return, the DUP secured a £1 billion-plus investment package for Northern Ireland.
From that moment on, the party, led by Arlene Foster, assumed a role of influence in the Brexit process that far outweighed its numbers on the Westminster benches.
– Theresa May’s deal:
DUP opposition to the agreement Mrs May struck with the EU in November 2018 was crucial.
Many other MPs voted against the prime minister on the three occasions she tried and failed to secure parliamentary approval but the outcome could well have been different if the DUP had backed it.
If the party had dropped its opposition to the Irish border backstop, there is an argument that several Tory Brexiteers would have followed suit, potentially giving Mrs May the numbers to edge a Commons vote.
But, for the DUP, Mrs May’s controversial backstop was something it just could not stomach.
For the unionists, an arrangement which would have seen Northern Ireland diverge from the rest of the UK on regulatory rules – without an obvious exit mechanism – undermined the constitutional integrity of the UK and created an economic border in the Irish Sea.
For the DUP, the Union comes above everything. Brexit has never been its raison d’etre; the Union of Great Britain and Northern Ireland is.
– Boris Johnson’s proposals:
The DUP was accused of performing a sharp U-turn when it backed Mr Johnson’s Brexit plan – proposals that also envisaged Northern Ireland in a different regulatory framework from Great Britain.
The party rejected the claim, insisting the difference with the new blueprint was a consent provision that would have handed the Stormont Assembly, and potentially the DUP itself, a veto on both the adoption of the system and its continuation.
The DUP welcomed the Prime Minister’s pledge, outlined in his letter to the EU, of another investment package for Northern Ireland.
The party was also happy with Mr Johnson’s plan for a UK exit from the customs union, as the backstop would have seen the UK remain in a customs union until alternative arrangements to ensure a free-flowing Irish border had been agreed.
– New deal:
Mr Johnson’s plans did not secure an immediate breakthrough, with the EU – and Ireland in particular – opposed to his proposals around consent and customs.
Intensive negotiations followed, leading to Thursday’s announcement of a new deal.
In order to get the agreement over the line, the Prime Minister had to give ground on consent and customs.
This was a bridge too far for the DUP.
The party was not prepared to countenance another trade barrier down the Irish Sea or give up its ability to veto the arrangements at Stormont.
Mr Johnson has until Saturday to change their minds before MPs once again convene at Westminster to decide the fate of a Brexit deal.