Imagine for a moment that Theresa May, needled on Twitter by someone from Ireland with 29 followers, replied with a mild jibe about our neighbour’s creditworthiness.  A few people would say: “Good on you, Theresa.”  Rather more would think it was time to send not so much for the men in grey suits as the men in white coats.

Now there is a difference between the Prime Minister acting in that way and the Taoiseach doing so, as he did yesterday.  Ireland will never have to help bail the UK out.  But the reverse doesn’t apply.  So a tweet to that effect from May would touch a raw nerve.  Leo Varadkar’s yesterday did not, and is thus a flight of fancy – and, like many such flights, has a kind of strange charm.  That his facts were questionable doesn’t detract from it.

None the less, it is odd that the Taoiseach should bother with Mr What’s-His-Name – unless, that is, you ponder the present state of Anglo-Irish relations.  Ireland’s Government is hopping mad with what it sees as the UK Government resiling from the backstop – a commitment signed up to by the latter in last December’s joint report by both parties to the European Commission.

The Irish Government has a point.  It has one, too, when one considers the natural meaning of that backstop – paragraph 49 of the report.

“The United Kingdom remains committed to protecting North-South cooperation and to its guarantee of avoiding a hard border. Any future arrangements must be compatible with these overarching requirements. The United Kingdom’s intention is to achieve these objectives through the overall EU-UK relationship. Should this not be possible, the United Kingdom will propose specific solutions to address the unique circumstances of the island of Ireland. In the absence of agreed solutions, the United Kingdom will maintain full alignment with those rules of the Internal Market and the Customs Union which, now or in the future, support North-South cooperation, the all-island economy and the protection of the 1998 Agreement.”

This cannot reasonably be read as both parties signing up the entire UK to a large swathe of Single Market rules plus the Customs Union, as some on this side of the Irish Sea have suggested.  The context makes it clear that our Government will be obliged to sign up Northern Ireland to these in the event of no other agreement between the UK and the EU being reached.   The drafting is presumably imprecise because the EU assumed that it is up to our Government, and not the EU itself, to ensure that this happens.  (Which, by the way, points to Northern Ireland’s status as part of the United Kingdom.)

But if the Irish Government has some arguments on its side then so does its UK counterpart, if it chooses to make them.

We won’t quibble about the phrase “full alignment”.  The natural meaning of this is “full regulatory alignment”, and this appears to be what Geoffrey Cox told that inner group of Cabinet ministers recently, when the provisional agreement that Olly Robbins had struck with his EU counterparts was put to them.

It is worth noting, though, that Downing Street officials assured Michael Gove, and others, of precisely the opposite last December, shortly after the joint report was signed.  “We’ll ensure Northern Ireland stays aligned with the Irish Republic in those areas necessary to keep effective cross-border cooperation,” he wrote in the Sunday Telegraph, during the days following the publication of the joint report – in an article cleared, as all such pieces must be, by Number Ten.  “Crucially, however, the UK Government has made clear that in those areas the UK continues to reserve the right to meet shared goals by our own means,” he added.

That last phrase can only mean divergence.  But that’s precisely what “full alignment” rules out.  No wonder the Environment Secretary said recently in Cabinet: “fool me once, shame on you.  Fool me twice, shame on me.”  Blame Gove if you like for believing those Number Ten officials in the first place.  But you will understand why he and others no longer trust them, and are insisting that the full meaning of any deal is set out for them by the Attorney General in writing.

So instead of tossing the meaning of “full alignment” back and forth, turn instead to the remarks at the head of the joint report, which provide the context for it.  “Under the caveat that nothing is agreed until everything is agreed,” it says, “the joint commitments set out in this joint report shall be reflected in the Withdrawal Agreement in full detail.”

And since everything has certainly not been agreed to date, it follows that nothing has been agreed.  This take is reinforced by the text of the Draft Withdrawal Agreement published in March.  The section which repeats the backstop is marked in yellow.  This means that “negotiators agreed on the policy objective. Drafting changes or clarifications are still required.”

David Davis pointed to the significance of the preamble on The Andrew Marr Show last December, when he was still Brexit Secretary.  That caused a row then.  But the point still stands now.

Next, turn to the what follows paragraph 49 of the joint report – namely, paragraph 50, inserted after back-and-forths between our Government and the DUP:

In the absence of agreed solutions, as set out in the previous paragraph, the United Kingdom will ensure that no new regulatory barriers develop between Northern Ireland and the rest of the United Kingdom, unless, consistent with the 1998 Agreement, the Northern Ireland Executive and Assembly agree that distinct arrangements are appropriate for Northern Ireland. In all circumstances, the United Kingdom will continue to ensure the same unfettered access for Northern Ireland’s businesses to the whole of the United Kingdom internal market.

So both the EU and the UK have agreed, subject to the usual proviso that nothing is agreed until everything is agreed, that our Government will ensure that there are no new regulatory barriers in the Irish Sea.  Now ponder the implications of putting paragraphs 49 and 50 together.

Riddle me, riddle me, riddle me ree.  If there are to be no new regulatory barriers between Ireland and Northern Ireland, and none either between Northern Ireland and the rest of the UK, and Brexit is to take place, how can either the EU or the UK establish a new regulatory border at all?  And if Northern Ireland is to be hived off into a separate customs territory from the rest of the UK, how is that compatible with the part of the Belfast Agreement which declares that “it would be wrong to make any change in the status of Northern Ireland save with the consent of a majority of its people”?

The backstop is not only conditional, like everything else in the joint report, on nothing being agreed until everything is agreed.  It is also self-contradictory – if, that is, paragraph 50 is considered alongside paragraph 49.

Theresa May’s view of the backstop, at least as outlined in the Commons yesterday, is incompatible with the EU’s.  But if opposites can be reconciled anywhere, then Northern Ireland must surely be a place of choice.  Given the impasses during the run-up to the Belfast Agreement; remembering how the DUP eventually went into government with Sinn Fein; and considering that the whole show is, despite the collapse of the administration there, just about still on the road – nothing will persuade this site that the backstop cannot be fudged to our Cabinet’s satisfaction.  The backstop is a high horse.  Dublin and London need to find a way of climbing off it.