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A total breakdown in talks with Europe—once dismissed as a vanishingly remote possibility—can be dismissed no longer. Theresa May and Jean Claude-Juncker can agree to “accelerate” their efforts at negotiation, but it is now at least conceivable that Britain could tumble over the Brexit cliff edge without any deal whatsoever.

In recent days, attention has turned to the political ramifications. Unlikely alliances have emerged: witness the delicate choreography between between Labour’s staunchly socialist Shadow Chancellor, John McDonnell, and the Tory veteran Ken Clarke, who respectively took to the airwaves last Sunday and Monday to let it be known that they were ready to work together to pull Britain back from the no-deal brink.

Excited scribblers were soon suggesting that a “no deal” crisis could even put the whiskered one from Islington in No. 10. Sky’s Political Correspondent Lewis Goodall is just one of the prominent journalists who indulged in this speculation, arguing that the political ruin of a bad Brexit could feasibly lead to “a period of Jeremy Corbyn in government.”

But he like many others has failed to think through the many practical steps that would have to be involved. So we thought we’d have a go—stress testing every one, to get a sense of whether there is a plausible path from the Brexit talks breaking down to a Corbyn administration.

Warning: there are a lot of “ifs” along the way.

Step 1: the talks must crash

A “no-deal” outcome would seriously disrupt cross-Channel trade and investment flows, and impose substantial costs on both sides. It would be unambiguously beneficial to both sides to, at the least, do the sort of deal the EU has done with Canada, which could allow commerce to continue without tariffs or other unnecessary disruption.

If cooler heads can prevail in London and Brussels they will, in the end, find a way to co-ordinate that. But there is the possibility that negotiations are beginning to run out of control—in a manner that gives the whip hand to the hot-heads.

There are murmurs on the continent that the way to hold the remaining Union together might be to administer a good kicking to the UK.

Indeed, in the draft declaration for this week’s summit, Paris and Berlin slipped in a clause about the continuing role of the European Court of Justice—something they are well aware is a red line for May’s hardline Brexit brigade.

Meanwhile, Eurosceptics at home seem keen that Britain should simply storm out soon. Readiness to embrace “no deal” is becoming a political virility test: give me freedom and give me death—as the founding fathers didn’t quite say.

“No deal” is still not the single most likely scenario, but could it happen? Well, in the words of one seasoned diplomat talking to Prospect, “of course.”

Step 2: Parliament secures a meaningful say

A bit of background is important here to understand the origins and the prospects of the current manoeuvres in Parliament. In a different political universe—all of eight months ago—Theresa May promised MPs something called a “meaningful vote” on her Brexit deal.

According to Professor Meg Russell of UCL’s Constitution Unit, this phrase was “decidedly ambiguous”—but it probably had to mean something with at least the appearance of substance, rather than—say—a purely procedural adjournment motion. Yet, Russell cautions, that is not “the same as saying that it would bind the government.”

Remainers and (briefly) the House of Lords got uppity when they subsequently discovered that, as May saw it, this vote was going to be on “my-way-or-the-highway” terms: if parliament didn’t like May’s deal they could instead vote to push the country over the edge with no deal at all. The woman who had made “Brexit means Brexit” her catch-phrase was now charged with proving that “meaningful” meant meaningless.

Some speculated about what would happen if May lost her vote: would Parliament really sit meekly by while Britain went over the edge, or would it push the PM off the cliff instead? But as the spring unfolded, all such questions came to seem immaterial, as the snap election was announced. The conventional wisdom held that the saboteurs would be crushed, and, irrespective of parliamentary procedure, May would win a decisive mandate to do as she pleased.

That, of course, was not to be. But even after the snap election, all discussion was still predicated on the assumption that there would be some sort of deal to go through the motions of a “meaningful vote” on.

A different question must today be asked: what happens if that assumption is wrong, and there is no deal at all?

Ostensibly, the May plan for handling MPs in this scenario would involve offering them a choice: between endorsing the government’s conclusion that “no deal” was better than the bad deals Europe had offered, or rejecting the government position and, nonetheless, tumbling out of the EU. A non-choice, then, between no deal and no deal.

In pure procedural terms, then, you can see why proud parliamentarians are now combining across party lines to try and take back a little control. But is this still possible? Russell warns that we are now in a world where “the government can lose some seemingly substantive motions and then ignore them.”

This has been happening on opposition day debates on domestic policy—which the government has brazenly announced it will simply keep its troops away from, lose and then ignore.

So how to give MPs real bite? “The surest trick,” said Russell, “is to write the requirements for extra safeguards and votes into law. And the most obvious law to go for is the Withdrawal Bill.” This legislation, previously marketed as the Great Repeal Bill, was meant to be heading into the committee stage, but progress has stalled. Consequently, it might not make it into the Lords until the new year, where it will likely remain under consideration until the Spring.

That could be the moment to pounce. Peers would do the handiwork of amending the bill, but with the blessing of concerned MPs. They could tweak it to ensure, for example, that the act of leaving the European Union would require one final fresh piece of legislation; unless and until this additional bill was passed, the law would assume we Remained.

MPs like Dominic Grieve, who has been pushing for exactly this change and would be well-placed to attract Tory allies, could then dig in against reversal in the Commons.

Step 3: Mayday in the Commons

Imagine now that May, or her successor, conclude that “no deal” was where we have got to by Autumn 2018. This has long been seen as the most likely parliamentary crunch point—it is the moment by which both Brexit secretary David Davis and his EU counterpart Michel Barnier have signalled they would need the outline of a deal to have been hammered out if there is to be any chance of legislating for it before Britain leaves the EU at the end of March 2019.

(Since the PM’s Florence speech, in which May conceded that Britain would be asking for a two-year transition deal, there is a bit more haze on the timing. But let’s stick with next year as the crunch point for illustration—not least because we don’t yet know whether the UK will succeed in getting its two-year transition, and furthermore because the Article 50 clock continues to tick down to exit in March 2019).

Now imagine that parliament has secured the right to that “meaningful vote.” The arithmetic would suddenly look frightening for the government. Don’t forget that three MPs in every four were originally for Remain. Sure, the majority fell into line with the referendum result, with MPs voting by 498 to 114 to allow for the triggering of Article 50 at the start of this year. But that was on the understanding that there would be an attractive “red, white and blue” Brexit deal, to use May’s phrase at the time.

If we moved to a world where that’s no longer on offer, and the choice is between “no deal” and Remain, then many MPs might drift back to where they started. Jeremy Corbyn, who has vowed not to block Brexit, would have presentational problems. But having set himself robustly against “no deal,” he could surely find a way to vote against this “Tory form of Brexit.” And with growing evidence that “no deal” would be deeply unpopular it’s not impossible to imagine support to Brexit shrivelling back down towards the original hard-core minority of Leavers. The best guess is that the vote would be lost.

Step 4: Regime change

If May had somehow survived until this point—brushing off the snap election, the crumbling of Cabinet discipline and the collapse of the EU talks—she would surely be out on her ear now, forced to announce she’d step down as soon as a successor was chosen. If she had already been replaced at this stage by another PM who had allowed things to get to the no-deal pass, a defeat in the Commons on this issue would probably finish them off, too.

The immediate question, therefore, would become who the Conservative party could turn to for a replacement—a Remainer like Amber Rudd, who may try and stop the Brexit clock while they figured out a way forward, or another Leaver, such as Boris Johnson. With the final decision in the hands of the diminished and anti-European ranks of Conservative members, the odds are on a Leaver coming out on top.

But, with parliament rejecting Brexit, where would a Leaver have left to go?

They could try and re-establish the failed EU talks, but Brussels would approach these on the basis that they were now dealing with an interlocutor who was even more hostile than May. Even if they got some traction, they would face remorseless opposition in parliament—from deep Eurosceptics who disliked the compromises involved in resurrecting a deal, and the now emboldened Remainers. In practice, the new PM would be governing against a hostile majority.

Step 5: Unfixing the Parliamentary term

The situation plainly couldn’t go on—but would it? In days gone by, fatally weakened governments have often limped on for far longer than they should have done: think of Jim Callaghan’s fag-end Labour government in 1978/79, or the painfully slow fizzling out of the John Major era between 1993 and 1997. Both governments survived multiple no confidence votes despite, by the end, lacking a majority; indeed, Major never lost one.

Things might be different in what would by now be a national emergency—it’s the kind of situation where parties do start to crumble, as happened, for example, in the financial crisis of 1931 from which the National Government emerged.

But this time, things would be greatly complicated—and the government greatly advantaged—by the Fixed-term Parliaments Act.

It is only possible to short-circuit this law—which currently stipulates that the next election will be in 2022—in two ways.

One route, used by May this Spring, is for a two-thirds majority of MPs to vote for dissolution. That is obviously not going to happen unless the bulk of the largest party, namely the Conservatives, wants it to. And why would they?

The alternative is for the government to fall in a confidence vote—and not just any confidence vote but one directed in specific terms laid out in the act—and for no viable alternative government to emerge in the following fortnight.

With no precedent to guide the Palace or anyone it is, as we’ve written before, entirely unclear who would get a go at forming this alternative government. It is not inconceivable that some new Conservative name—perhaps one willing to work across party lines—would be given a go.

There is, however, some chance that Corbyn would be summoned to put together a government, and put it to a vote of confidence. With just 262 MPs he’d be almost certain to lose—even without resorting to the scrappy but available tactic of constructively voting no confidence in himself. Only with the loss of this vote would another election be triggered.

Step 6: Europe re-enters the picture

Sometime around this point, between the change of prime minister and the fresh election, the attitude of the rest of the EU comes into play. Would it be ready to show some flexibility which could give a new prime minister, or more pertinently in an election campaign an opposition party, some room for manoeuvre? Many of Corbyn’s hopes would depend on it doing so.

We’re already in seriously hypothetical territory here—the government has failed to get a deal, failed to sell its no-deal Brexit to MPs, and then fallen in a confidence vote. There are more Big Ifs to come.

The most pressing need of the UK would be for more time—Corbyn would be frantically playing for it. But before giving him any ground, the authorities in Europe would first need to reach a settled view on whether or not all the backsliding in Britain counted for anything in legal terms. Parliament may have voted against no-deal on the understanding that this would stop the Brexit clock, but does London have the authority to do that?

Lawyers dispute how much room we’ve got for a rethink. Some are extremely confident that we can still change our mind right up until the clock runs out. Last month the man who originally wrote Article 50, John Kerr, stressed to us “Of course you can take it back!” You might think that he should know.

But it’s not up to him; it may be that, having set the Brexit clock ticking, we have no way to stop it. Lawyer and Financial Times commentator David Allen Green tweeted recently that the UK had “lost control with the article 50 notification.” His position is nuanced—but the general idea is that Britain cannot simply “decide” to revoke A50; other European powers might have something to say. Even those who are convinced that London can, in the jargon, “unilaterally revoke” mostly concede that a ruling by the European Court of Justice will be needed to make this clear in the coming months.

If the ECJ ruled that Britain had locked itself in, then any extension of the Article 50 clock would need to be unanimously agreed. Any one of the other 27 Member States could throw a spanner in the works. Some country or other might always have a reason for making trouble—dramatically reducing the scope for anyone on the continent who wants to cut Corbyn some slack to do so.

But if Kerr is right, and the opposition can still pull Britain back from the brink, then the views of Jean Claude-Juncker, Emmanuel Macron and Angela Merkel would come suddenly to the fore in British politics.

With the talks broken down, there would already be a lot of angry nationalism in the air. If—fed up with Britain—the European leaders resolved to offer no favours, unless Britain about-turned and embraced permanently Remaining, Corbyn could find himself boxed in. He’d be left with the same stark choice between a “no deal” he had said is unacceptable, and disregarding the referendum he had vowed to honour.

Dodging the dilemma, as he has successfully done until now, would no longer be an option: he would be forced to choose to make a call which could shatter Labour’s fragile unity, and would then, very easily, find the election just as punishing as the Conservative party.

Alternatively, however, the powers that be on the continent could signal that, in the right circumstances, they would be willing to at least consider a radically different deal—perhaps involving some sort of revised membership or special status for Britain. With the Conservative party led by a Leaver, this would provide Corbyn with a lifeline that could carry him through the campaign.

Step 7: Winning the election

Corbyn confounded expectations in June—but those expectations could not have been lower. He persuaded millions of extra people to vote for Labour, but did so at a time when the media was saying there was simply no hope of him reaching No 10. His radical anti-war stance in foreign affairs would now attract much more scrutiny, and so would questions about whether his manifesto pledges added up. A career oppositionist could find campaigning on the threshold of power extremely tough.

Despite the Tories’ weakened position the Labour Party is, today, still tending to poll only a touch above them. After Labour built piles of votes last year in its inner-city heartlands, the electoral system favours the Conservatives, too. And, however shattered her authority might be, May still sometimes has the edge on Corbyn when it comes to personal ratings. There is every chance that a new and less-damaged face for the Tory tribe would have a more decisive edge in the leadership stakes.

Nobody, in sum, would be well-advised to predict how a next election fought in conditions of a national emergency would go. The obstacles to the man from Islington coming out on top remain numerous and formidable. But after so many wrong predictions about politics in the last few years, it would be rash to deny there is, at least, a conceivable path that could lead from the Brexit cliff edge to Jeremy Corbyn’s Britain.