Let’s get a few things straight. There is a cohort of around 50 Tory MPs who want a No-Deal Brexit because they want the UK to deal with the EU and the rest of the world on a WTO terms basis. This aim is completely inconsistent with an All-Ireland economy which is central to the Good Friday Agreement.

This group of Tory MPs does not care about the Good Friday Agreement, the border, or peace and reconciliation on the island of Ireland.

They have convinced themselves that the integrity of the United Kingdom and its unwritten constitution requires that Northern Ireland’s relationship with Ireland and the EU precludes any special economic or regulatory regime for the North.

Insofar as the United Kingdom has a constitution at all, as distinct from a series of long-standing but alterable conventions which can be changed at the will of Parliament, these Tories seem to forget that they have already elevated to constitutional status the Good Friday Agreement which, among other things, makes it clear that the continued membership of the North as part of the UK depends upon the will of a majority of the people of Northern Ireland and that the North will cease to be a part of the UK is a majority of Northerners opt for a united Ireland.

If you want a document which is part of the UK Constitution, look no further than the Good Friday Agreement. Not merely was the Constitution of the Republic amended to accommodate it, but Britain registered this solemn agreement at the United Nations.

The Good Friday Agreement, and not some Westminster statute, is now the key constitutional document defining the status of Northern Ireland and defining the terms in which the north’s sovereignty can change.

So when you hear talkative MPs querying whether a majority of MPs can properly take over the conduct of the Brexit process from a government lacking a parliamentary majority on the subject, and when you hear them claim that the parliamentary business at Westminster must, as a matter of constitutional imperative, be determined by Her Majesty’s Government, a rule of parliamentary procedure is being elevated above the wishes of a temporary majority in the House of Commons and is being accorded a sacrosanct status which it doesn’t deserve.

Just as in Ireland, the Dail accords the government a leading role under its Standing Orders in deciding the business agenda of its sittings, that aspect of Standing Orders is not of constitutional status and is liable to be overridden by a motion headed by the words “Notwithstanding anything in Standing Orders, …”.

A majority in the House of Commons is free to take over the reins as it sees fit to ensure that its will is implemented.

The false equivalence of parliamentary procedures and conventions with the United Kingdom’s constitution demonstrates a complete absence of understanding on the part of the Tory hardliners of the nature of parliamentary sovereignty in the United Kingdom.

Moreover, that false equivalence which seems to accept that Britain has no constitutional duty to uphold the Good Friday Agreement if the House of Commons prefers to allow the UK to crash out of the EU on a No-deal basis demonstrates profound ignorance of the constitutional status of Northern Ireland since the Good Friday Agreement.

All this would be very obvious were it not for the alliance of convenience between the hardline WTO Brexiteers and the DUP.

We have to remember that the DUP was not an original party to or adherent of the Good Friday Agreement. Many senior DUP members disliked the Good Friday Agreement and regard it as something which was imposed unfairly on the Unionist community in the North.

There is a strange symmetry between the DUP and Sinn Fein; both parties have a visceral antipathy to the principles of the Agreement and each of them really wishes that the Agreement would simply go away.

If Teresa May is to win the approval of any majority – cross party or not – for any withdrawal agreement, she must either acquiesce in the ambitions of her WTO hardliners and their temporary allies in the DUP or, alternatively, find sufficient support across the House of Commons for a withdrawal agreement which does not command the hardliners’ support.

While there are some signs that the Labour Party might be willing to support a withdrawal agreement which was combined with a political statement of intent to have some form of EU/UK relationship similar to a customs union arrangement, Mrs. May’s problem is that such a withdrawal agreement will definitely lose the support of her hardliners and may only possibly attract the support of the DUP.

It isn’t clear whether the DUP would, if they were outvoted by a moderate Tory-Labour majority, withdraw all future support from Mrs. May’s government. If they were of a mind to withdraw their support for the Tory government, the question arises as to whether they would push the matter as far as a general election or would simply retreat into the political jungle to wage guerrilla war against a minority government from then onwards.

It is conceivable that a withdrawal agreement coupled with a political declaration committing the EU and the UK to some form of customs union relationship could have majority support in the Commons from moderate Tories and moderate Labour MPs.

It is even conceivable that such an arrangement, which could definitely avoid a hard border on the island of Ireland or some form of invisible border in the Irish Sea between the North and the rest of the UK, might be acceptable to the DUP.

If the DUP voted for or abstained on such a withdrawal agreement motion in the House of Commons, the alliance between the WTO No-deal Tory Brexiteers and the DUP would come to an end.

However, the DUP could still hold the balance of power for the remainder of this parliament’s term once such a Tory/Labour compromise was voted through.

The EU 27 is not going to accept a qualification of the backstop or a temporal limitation on it if the resulting situation gave the hardline WTO Tories a new opportunity to take the Belfast Agreement hostage and to use it as a bargaining chip in extracting concessions from the EU 27 in the next phase of negotiations on the future economic relationship between the EU and the UK.

The way things are going, it does not appear that the backstop will be jettisoned, diluted or time limited. If there really is some “alternative arrangement” which delivers the substance of the backstop and clearly prevents the Good Friday Agreement from becoming a bargaining chip in the next phase of EU-UK negotiations, we have yet to hear of it.

As I wrote here last week, Mrs. May has found out the hard way from her visit to Brussels that it takes two to tango. The EU simply will not dance to the tune of the Tory hardliners.

Mrs. May has her work cut out. It isn’t a matter of Ireland holding its ground in some obstinate or retributive political stance. Upholding the Good Friday Agreement and ensuring that it is not shredded or damaged by a small parliamentary rump which has little or no regard for it is an existential Irish interest.

Reneging on the backstop would deliver into the hands of future UK negotiators an immensely powerful lever which the EU 27 could not resist if it seeks to preserve the character of the EU including its single market.