If this Government is to endure until 2022, then it is very likely that Theresa May (or her successor) are going to have to renegotiate the Conservatives’ pact with the Democratic Unionists.

This was made almost inevitable by the fact that the two sides’ parts of the original deal were out of sync. The DUP pledged to support the Government for the lifetime of this Parliament – but the £1 billion ministers put up to secure the agreement will be fully paid out by 2019.

If taken at face value, this means that for three years the Prime Minister’s majority will be underpinned by little more than gratitude. But as Sir Humphrey put it: “Gratitude is merely a lively expectation of favours to come.” The deal provides that it may be reviewed “by mutual consent of both parties”, and such a review seems probable.

So how might that go?

One possible outcome is ‘much the same as before’. Assuming that they have successfully helped to steer the Government towards a Brexit which respects the UK’s territorial integrity, the DUP could simply try to exploit the Tories’ precarious position for another round from the pork barrel. Perhaps the Chancellor should commission some research into that giant bridge.

But Brexit won’t be the only major change in circumstances which ought to weigh on the minds of DUP decision-makers. With the Northern Irish Office’s wait-and-pray approach to restoring devolution rapidly running out of road, it seems likely that by 2019 the Government will either formally or informally have implemented some form of direct rule.

Such a move would have the effect of dramatically increasing the importance to the DUP of its Westminster relationships. And if the Secretary of State takes the expected step of using direct rule to bring Ulster’s abortion and gay marriage laws into line with the mainland (thereby absolving the DUP of the need to do it themselves), some of the most significant barriers to a deeper relationship with the Conservatives could be neutralised too.

Many in the DUP will be wary of taking such a bold step. Some simply aren’t conservatives, whilst others fear that they may suffer the same fate as the Liberal Democrats – although since the Tories cannibalised most of the Lib Dem vote and don’t stand in Northern Ireland, that seems unlikely.

But they have much to gain, not least how badly the sight of Northern Irish MPs serving in government would highlight to nationalist voters the steep cost of supporting Sinn Fein, who refuse to take up their Westminster seats, during a period of direct rule.

Serving in Government would also give the DUP a precious shot at bridging the gulf which has opened up between Northern Ireland and the mainland during the decades when the Province’s politicians were stuck behind a firewall in the ‘Others’ column, not to mention an opportunity to influence the Government’s often-lamentable understanding of the Belfast Agreement.

For the Tories, who have made so much of their unionist credentials over the past few years, the upsides are also clear: better integration of Northern Ireland into the broader political, economic, and social life of the UK, and a lasting boost to the tune of between eight and twelve seats in the House of Commons.