As irony would have it, the patriotic razzle-dazzle of yesterday’s royal wedding capped the worst week for Brexiteers since Britain voted to leave the EU almost two years ago.

To understand why, think on to six months or so after that referendum, and look again at the speech in which Theresa May first set out her renegotiation aims.

Announcing that Article 50 would be moved the following spring, the Prime Minister proclaimed Global Britain – “our ambitious vision for Britain after Brexit”.  Britain would “look beyond our continent and to the opportunities in the wider world: “that is what the country voted for”, she told the Conservative Party Conference.

The following January at Lancaster House, she spelt out what this would mean in more detail.  Exit from Single Market membership.  Exit from the Customs Union.  (“I do not want us to be bound by the Common External Tariff.’)  “I am clear that no deal for Britain is better than a bad deal for Britain,” she told her audience.  In case anyone had missed the theme of that first speech, “a vision of a Global Britain”, she opened this second one with the heading: “a Global Britain”.

That destination will fade to vanishing-point if last week’s Cabinet committee agreement on the UK/Ireland border backstop is implemented.  And it is difficult to see how it won’t be.

Driven by fear of losing DUP support, with the consequent collapse of her Government – and doubtless too by genuine Unionist conviction – the committee reiterated that there must be no east-west border in the Irish sea.  What applies to Northern Ireland must also apply to the rest of the United Kingdom.  As last December’s UK/EU agreement puts it, “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”.

The EU view is that “full alignment”, a phrase with no legal meaning, is nothing less than “full regulatory alignment”, which most certainly has one.  It is also that almost any aspect of the Single Market can be brought within this definition.  To cut to the chase, the EU take is that the backstop would see the UK bound to the rules of the Single Market in manufactured goods and agriculture.

And while it would remove us from the Common Commercial Policy – i.e: leave us at liberty to negotiate and ratify trade deals – the backstop would not, please note, free us from the Common External Tariff.  This would stifle the incentive for non-EU countries agreeing those deals in the first place.  Why do so when they would have to pay EU tariff rates on their goods?

In short, the backstop effectively places regulation for manufactures in the first of the Government’s proposed three “baskets”, whereby we align to EU ends by the same means – but with no possibility of divergence.   Britain remains bound to the Single Market, the Customs Union and the EU economies.  The Prime Minister’s original vision of a free-trading Global Britain vanishes, like Prospero’s masque in the Tempest: “The cloud-capped towers, the gorgeous palaces, / The solemn temples, the great globe itself – / Yea, all which it inherit – shall dissolve, / And like this insubstantial pageant faded, / Leave not a rack behind.”

There is more.

If the backstop kicks in, the Government, you could argue, will at least maintain control of immigration.  But the EU will doubtless claim that if the UK is to remain bound to the freedom of movement in goods, it must also be bound to freedom of movement for people.  And what will the dispute resolution mechanism be in relation to full regulatory alignment?  The EU will push hard to make it the European Court of Justice, or at least to give the court some formal role.

Now you may say that all this will only take place in the event of the backstop kicking in – “in the absence of agreed solutions,” as last December’s text has it.  This brings us to the heart of the matter.

If the UK and the EU reach a deal, it will be formalised in a Withdrawal Agreement before the end of next March, when Brexit takes place, and then enshrined here in a Withdrawal Act and in treaty acts.  But there will not necessarily be a fully-fledged free trade deal by then. That’s the way the negotiation works.

In other words, the EU will be able, if a withdrawal deal and agreement is reached, to keep stalling, if it wants to, on that elusive trade deal – after March next year and on into the future.  In which case, the backstop would kick in.

All this adds up less to Canada Plus, let alone Plus Plus Plus, than Norway Minus – EEA lite.  Readers will remember that, as Home Secretary, Theresa May took Britain out of 135 criminal justice measures only to opt us back in to 35 of them.  The backstop would be a version of the same process (though perhaps without the ECJ having a formal role).

You may now ask: why are David Davis, Liam Fox, Michael Gove and Boris Johnson – let alone the 80 or so strong European Research Group (ERG) of Conservative MPs – putting up with all this?

There are several answers, some of them good ones.  One is that the EU itself is very unhappy, at least in some quarters, about the backstop – which can be seen as cherry-picking on a grand scale.  It worries about the mirror image of an issue we sketch out above – i.e: the UK getting access to freedom of movement for goods without conceding freedom of movement for labour.

Another is that we may somehow get that trade deal before next March, after all, rendering the backstop irrelevant.  David Davis is pushing hard for this, hence the promise of a White Paper soon on our post-Brexit future.  And for mutual recogniton of different regulatory regimes to prevail. Another still is that May and her Government may fight off a formal role for the ECJ.

However, there are other reasons that have less to do with the sweep of high policy than the skullduggery of low politics.  Brexiteer MPs could seek to force a leadership challenge.  But the ERG is divided about what to do.  In any event, it doesn’t represent all the 129 Tory MPs on record as having backed Leave.  May might, if challenged, sweep a ballot anyway – thus strengthening a Prime Minister that most Conservative MPs, and over half our panel of Party members, believe should stand down before the next election.  And were she to be deposed, some say, why would anything change?  A Prime Minister Johnson or Gove would still face a Commons in which most MPs voted Remain.

But there is another factor at work which is less political than psychological.

It is not so long since May declared that No Deal would be better than a Bad Deal.  But a year and a bit is a long time in politics.  Most Tory MPs and many Brexiteers have stopped believing that No Deal is possible – almost without thinking about it.  Perhaps the reason is that the December Agreement persuaded them that the EU will compromise; that it believes it has enough problems to be going on with without a disorderly Brexit on its north-west frontier.  (Our panel approved of the deal by a comfortable margin.)   Maybe a fear of Corbyn’s Labour is the driver.  Perhaps there is a weariness with the whole process.  Maybe there is a sinking realisation that there is no Commons majority for “the WTO option”.  Perhaps the core thought of pro-Leave MPs is: “let’s get through to Brexit Day. Once we’re out, then we can have ‘one more heave’.” This site will write more about that tomorrow.

However, it is hard not to conclude, as one mulls over the events of this year – the Chequers summit, Downing Street’s push for the customs partnership, last week’s committee agreement on the backstop – that May is slowly boiling the ERG frog.  A furtive twitch of the dial is more effective than a frantic wrench.  Gently does it.  And talking of keeping a low profile: where’s the Chancellor?