If we are honest, we all experience the feeling at some stage in our lives. And it is an awful gunk. You go to a disco or function with someone. Things seem to be going swimmingly. But then they disappear out a side door with somebody else and you are left high and dry.

Early this morning the DUP learned a horrible lesson about Boris Johnson. The aftershock is too raw at the moment from them to understand this as a case of "tough love".

What they have discovered to their cost is that Boris is promiscuous, politically.

The friendship wasn't expected to take this nosedive. Think back to February 2016 when as Mayor of London, Boris travelled in the company of several DUP members, including the local MP Ian Paisley Junior; Deputy First Minister Arlene Foster and Enterprise Minister Jonathan Bell (then inside the fold) to the Wrightbus Plant in Ballymena.

Boris posed for the cameras and even did a swing from one of the buses, Incredible Hulk style. Watching on smiling, was the then Secretary of State for Northern Ireland, Theresa Villiers, who would later become a key Brexiteer. Boris announced an investment of £62 million for a selection of the buses for London.

Under the Boris Bus in February 2016

Move forward to 24 November 2018 when the DUP relationship with the British prime minister, Theresa May, was under strain but the party was still propping up the minority Conservative party government in Westminster. Who is the star turn at the DUP Annual Conference on the outskirts of Belfast? The pretender to the throne - Boris.

The DUP indicated time and time again that support couldn’t be given to Theresa May’s Withdrawal Bill in Westminster. Reluctantly, but effectively, the actions of the DUP 10 effectively took out the Prime Minister. The phonecall Arlene Foster made from Co Fermanagh to Theresa May was decisive. When Boris emerged from the very weak pack, the DUP and their App group colleagues in the ERG were elated.

Earlier this month the Boris/DUP relationship was on public display when he turned up at the party’s reception in Manchester, on the fringes of the Conservative party annual conference.The speeches could barely be heard over the chants of " Boris, Boris."

But while that was in full flow, another passion play was beginning.

Remember 9 September, when Taoiseach Leo Varadkar welcomed Boris to government buildings in Dublin? The significant Garda cordon made sure there was no Luxembourg of House of Commons style gang of protestors roaring insults while the two prime ministers addressed the media. This was a very genuine public get together between neighbours, faced with a common challenge.

Another passion play was beginning in September 2019

And then recall last Thursday, just a week ago, when Leo travelled over to Liverpool – a very Irish city on the mainland – and held three hours of talks with the British prime minister. Hindsight is such a wonderful tool – we can now see the extent of the gamble, the engagement and the opportunity the Taoiseach was creating for the British prime minister.

The simple truth is, in Westminster terms, Boris was boxed in. The shock and awe strategy of Dominic Cummings was creating lots of tension and noise. But it wasn’t offering a fighting chance of leaving the EU as promised, Deal or No Deal on 31 October. The odds were increasing of Boris actually dying in a political ditch.

Leo Varadkar, possibly with a nod from some Europeans, offered him a less precarious option. While Dominic Cummings wasn’t across a lot of the face-to-face Liverpool discussions between Leo and Boris, and then when their officials were added, he obviously saw the Varakdar ladder just might have some benefits.

Again, with hindsight, some of the most difficult facts for the DUP to stomach are that they discreetly encouraged Boris to come to Dublin, their agreement to compromise on regulatory alignment gave momentum to the Plan B and the changed dynamic, supported by the DUP, helped to give substance to the project that reached fruition in Brussels today.

If there was a turning point it was a week ago when the DUP deputy leader, Nigel Dodds, suggested on the consent issue that Stormont unionists would be able to exercise a veto. Effectively, he was saying that a minority would be able to hold sway over the implementation of elements of the EU’s Single Market policy. And that minority he had in mind (the DUP/unionists) would be avowed Brexiteers, no longer members of the European Union. The structure he was using to justify the minority veto arrangement was the Good Friday Agreement – something the DUP did not support in 1998.

"It wasn't a case of him throwing the DUP under the bus - but the Boris bus certainly left the station without the DUP on board"

It was the new Secretary of State for Northern Ireland who quickly said no one party or faction would be able to exercise a veto on the consent issue. Historians, note the name of Julian Smith. His predecessor, Karen Bradley, a friend of Theresa May, had been given instructions to keep the DUP sweet, as their votes were needed in Westminster. Julian Smith, a former chief whip, a Remainer, had the active support of the DUP when he was given the Northern Ireland Secretary role. He has done more in a few weeks than the combined impact of his predecessors over several years.

And so it came to pass that Boris headed off to Brussels this morning with the DUP saying, hold on we are not finished yet. It wasn’t a case of him throwing the DUP under the bus. But the Boris bus certainly left the station without the DUP on board. Power politics took over. A summit of the leaders of the European Union had been organised. Boris had his slot, his moment in history and the time for haggling over branch office matters was over.

Boris and Arlene in happier times

Whither now the DUP? In terms of their relationship with their former VBF (very best friend) Boris, the last line of their statement, issued this afternoon, is ominous."Saturday’s vote in Parliament on the proposals will only be the start of a long process to get any Withdrawal Agreement Bill through the House of Commons", it said.

That suggests that rather than accepting what has happened and making the most of Boris guilt to work up a compensation arrangement, the DUP is intent on digging in. Its 10 MP’s may well vote against him or abstain on Saturday next. A British general election seems inevitable, this side of Christmas. Boris and Dominic Cummings know that. They also may be working on the premise that they have a fighting chance of coming back stronger, particularly if fences are mended with some of the Conservative MPs who were on the receiving end of shoddy treatment.

Leo Varadkar enjoys smiling. He practices it quite a lot. He is entitled to be smiling this weekend. But when the DUP anger subsides, relationships will have to be rebuilt.

Arlene Foster, like Michelle O’Neill, is a devolutionist. Someday in the not too distant future the pair of them may get a chance to make history as Northern Ireland’s first female leadership team in the Assembly. Nigel Dodds and his 9 DUP Westminster colleagues will soon contest a general election. Some, maybe not all of them, will be returned. Boris might well get a mandate to take over as British prime minister. The next chapters of the Brexit drama will begin to unfold.

Time indeed is a great healer. Nobody goes through life, particularly political life, without a belt. Today was the DUP’s turn.

Leo, take note.