Here is a worst case scenario, or at least a very bad one.

Boris Johnson is torn between Joe Biden and his backbenches.  He might be up for a trade war with the EU, but he isn’t for a diplomatic one with America’s president too.

Ditto the Cabinet, with the exception of David Frost, though not at all so of Michael Gove.

So the Government does not trigger Article 16 of the Northern Ireland Protocol.  Nor does it further extend the present grace periods that relate to it. Neither does it legislate to ensure that the Protocol no longer has effect in domestic law.

Nonetheless, a revived European Research Group, which originally swallowed the Northern Ireland Protocol in order to gain Brexit, now vomits it up again – saying that it’s now clear that the Protocol is unacceptable to a broad swathe of the province’s Unionists.

So the Prime Minister serves up a compromise solution which effectively aligns the UK’s animal and plant rules with the EU’s, and establishes border checks to police the system.

Unsurprisingly, this turns out to satisfy no-one.  The problem of shortages lessens.  But those of checks grow – because loyalist paramilitaries begin to target facilities and staff, doing at the sea border what the IRA once did at the land one.

Frost quits.  The ERG cross-fertilises a revolt of its own with the backbench rebellions elsewhere – on overseas aid, say, and on housing.  The uptick in the Government’s fortunes turns into a downtick, which gains further momentum from post-lockdown policy challenges.

Meanwhile, unionism in Northern Ireland continues to fragment.  The DUP loses support at both its ends – some to the Alliance, some to Traditional Unionist Voice, some to new breakaway movements.

The prospect of a Sinn Fein First Minister in the wake of the province’s Assembly election grows.  Which paralyses the Executive, if it doesn’t collapse completely.  Working relations between DUP and Sinn Fein Ministers break down.

Big issues in Northern Ireland – legacy issues, the Irish Language, tackling paramilitarism – remain unresolved.  The Troubles start up again, though at a less intense level.

There is pressure from the nationalist end for a referendum on Irish unity.  Perhaps one takes place and perhaps one doesn’t.  If it does, Northern Ireland votes to stay in the UK, but not by a large enough margin to guarantee no second referendum in the near future.

It also becomes clear that, in the wake of any referendum vote for Irish unity, Northern Ireland faces the possibility of re-partition, with an orange statelet running in an arc down parts of the north and east coast, including bits of Belfast.  And ethnic cleansing.

In short, history repeats itself.  Loyalism always becomes more militant when its supporters believe they are being sold out – as during the years after the Anglo-Irish Agreement, when paramilitary violence rose; or in 1913, when the original Ulster Volunteer Force was founded.

UK governments have no recent history of resisting sustained pressure from American ones.  We are thinking less of Suez than of the role that Irish-America played during the run-up to the Belfast Agreement.

And for all Randolph Churchill’s pugnacious rhetoric, and later Conservative sympathy for the Ulstermen, the Tory Party ultimately took the loss of Ireland itself on the chin.

Furthermore, events in Northern Ireland now take place in parallel to those in Scotland, and the threat of a second independence referendum that will return a Yes decision.

So what happens next in this cheerless scenario is scarcely surprising.  For all the ERG’s words and votes, the Tories gradually take on more of an English nationalist flavour.

You’re determined to align Northern Ireland to your rules, they ask EU politicians and commissioners?  Very well, they say.  You police the Single Market among a mass of seething loyalists, and good luck to you.

You’re up for a united Ireland, they ask Irish nationalists?  Fine.  Let Ireland’s armed forces and police try their luck in Portadown, Tiger Bay and Ballymoney.  Oh, and talking of money, you and your friends in America can stump up for more of the Bill.

You want us to work with you on an Atlantic Charter, they tell the Biden administration.? Of course.  And, as we’ve seen, the Government is unwilling to antagonise the President.

But the Conservatives don’t really have their heart in it.  Meanwhile, Government attitudes to Vladimir Putin take on a more Faragiste tone.  Ministers become more willing to work with Viktor Orban in Hungary and with Poland’s Law and Justice Party.

None of all this is inevitable.  Indeed, this grisly scenario may not happen at all.  There is no intrinsic reason why it should – since, in our view, the Protocol is workable if applied minimally.

Perhaps all concerned can muddle through: after all, the Belfast Agreement is an exercise in muddling through, and not usually the worse for it.

If, however, the EU seeks a maximalist solution; and if Joe Biden, of whom we had hoped better, simply backs it up – thereby applying a different standard to republican and loyalist dissent…

…Then both risk managing more of the consequences themselves.  “You broke it, you own it” is a double-edged sword.