One: the European Union and/or the Single Market ceasing to exist.

This is highly unlikely.

Two: Ireland leaving the European Union and/or the Single Market.

This is also highly unlikely.

Three: the United Kingdom rejoining the European Union.

This is unlikely at least for a political generation - and it would require the European Union wanting the United Kingdom back, which given our ongoing political psycho-drama is difficult to envisage.

Four: Northern Ireland not sharing a Single Market with Ireland.

This is unlikely, as it would mean a trading border, and perhaps even border infrastructure, on the island of Ireland.  Some would say that such invisible and visible borders would be a breach of the spirit, if not the words, of the Good Friday Agreement.

Five: the United Kingdom as a whole sharing in the Single Market, even if formally outside the European Union.

This was the preference of some "liberal" Brexiters and it was also pretty much the (infamous) "backstop" position of the withdrawal agreement negotiated by Theresa May, the last-but-two of our recent prime ministers.  That agreement was voted down by Parliament and led to a change of Prime Minister.

Six: Northern Ireland sharing a Single Market with Ireland, but not the rest of the United Kingdom.

This is the current position under the Northern Irish Protocol, negotiated and promoted as an "oven-ready" agreement by Boris Johnson, the last-but-one of our recent prime ministers: the trade border down the Irish Sea.  This is not acceptable to the Democratic Unionist party and some government backbenchers.

Seven: a united Ireland.

This would at, a stroke, resolve the matter of Brexit and the island of Ireland.

Given the first two options are literally incredible, the third is unlikely in the short-to-medium term, and the fourth is politically impossible, that leaves the final three.  As the fifth and sixth do not have settled political support, that leaves only the seventh.

Many of you will prefer the United Kingdom to re-join the European Union, or at least the Single Market; and my own first preference is for a united Ireland, with participation in the Single Market for Great Britain by means of a close association agreement.

I quote him at length because I regard him as representative of mainstream establishment thinking in England. He is generally supportive of the British unwritten constitution, if appalled by Boris Johnson's attempts to circumvent it. He is agnostic on Brexit, but anxious to make it work as well as possible for Britain. I do not know his party affiliation (if any) but he describes his "Law and Policy Blog as providing Independent commentary on law and policy from a liberal constitutionalist and critical perspective. "

He used to work as a government lawyer and cannot be dismissed as some far left or far right headbanger. If he has come to the logical conclusion that the best alternative to the current impasse over the Protocol is a united Ireland, you can take it that that could become the gathering consensus amongst the English legal and political establishment more generally.

In  Protocol deal in DUP's best interest. Thing is, they just don't know it yet, former senior Irish Ambassador and diplomat, Bobby McDonagh, comes to a similar conclusion: noting that nothing would be more likely to drive support for a Border poll than significant disruption of North-South relations and co-operation, and I quote:

Most obviously, it is in the interests of unionism that Northern Ireland is seen to work. By definition, that is a core objective of unionism. It can hardly be claimed that Northern Ireland is working effectively as long as the institutions of the Belfast Agreement are in cold storage, and if decisions affecting the people of Northern Ireland are taken either by civil servants or by the London government with input from Dublin. That is not to apportion blame for the present impasse. It is simply to observe that, in the longer run, effective functioning of the region as an integral part of the UK is a more fundamental priority for those who want to retain the constitutional status quo than for those who want to change it.

My point is simply this: If senior establishment figures on both sides of the Irish sea are coming to the conclusion that if the DUP rejects whatever compromise solution to the operation of the protocol is negotiated by the UK government, the case for a united Ireland will only get stronger. And if both establishments come to that view, they will have ways of making it happen. The current majority for the status quo in Northern Ireland could be persuaded to change their minds if that status quo is made sufficiently unattractive to them by way of savage austerity cuts.

I don't want to overstate this case. For the time being the ERG may be able to provide the DUP with sufficient political cover to either stay Sunak's hand, or to reject his deal. What is certain is that there will be no more negotiations by the EU if the deal is rejected. We are then on the slippery slope towards trade sanctions if the UK continues to refuse to implement the protocol or enacts the Northern Ireland Protocol Bill.

What effect this would have on the UK body politic is difficult to predict. Perhaps the British people would rally around the Conservative government if it were seen to be bravely resisting punitive sanctions by the EU. Or perhaps there would be a more general reappraisal as to precisely why the UK is allowing its relations with its most important trading partner to be thrashed by a small party in Northern Ireland.

Conventional wisdom has it that Britain will not wish to move towards a united Ireland for fear of exciting nationalist sentiment in Scotland. Paradoxically, however, if a move towards a united Ireland were to come to be seen as immensely problematic for both Ireland and Northern Ireland, it might put a dampener on nationalist sentiment in Scotland. Some canny Scots may opt to take a "wait and see" approach to independence, lest Irish re-unification turn out to be the disaster may unionists predict.

All of this is speculation, and none of it may come to pass. But the DUP needs to be aware that rejecting whatever compromise deal Sunak comes up with carries severe long term strategic risks for the Union. The ERG may have their backs, but they may not be around as a pivotal force in UK politics for very much longer. Unpleasant and unpalatable as the compromise deal may be, especially when combined with the prospect of serving with a Sinn Fein First Minister, it may end up as the only game in town if the Union is to be preserved for much longer.