The only certainty in the Brexit process is that there is no certainty. Brexiteers had long sought solace in the fact that, by law, the United Kingdom will leave the European Union on 29 March with or without a deal. But it’s now clear that this is not necessarily the case — or even likely. As we have seen this week, Theresa May is not in control of her party any more than Jeremy Corbyn is in control of his.

Corbyn has been forced to move towards the idea of another ‘public vote’ on Brexit, though he has no enthusiasm for one, because he fears that if he doesn’t, MPs would leave his party and join the new Independent Group. Fear of ministerial resignations drove May to say that MPs will have the right to oblige the government to request a Brexit extension if her deal is defeated, further weakening her negotiating position. The parliamentary maths is such that the Commons is almost certain to vote to request an extension to the Article 50 process rather than simply leaving on 29 March.

May is now suggesting that any extension would be only a short one, until the end of June. Brexit, the argument goes, must be complete before the new European Parliament starts its term on 2 July. But this, too, is fanciful. If the numbers don’t exist in the UK parliament for a no-deal Brexit at the end of March, they won’t suddenly appear by June. The Prime Minister is essentially admitting that the Commons won’t let the UK leave without an agreement. Brexit can happen only if a deal passes.

Any extension will be a humiliation for the Prime Minister, who has repeatedly said that Britain is leaving the EU at the end of March, come what may. But on the upside, it improves her chances of winning the next big vote on her deal, due on 12 March; and that is now the only way of Britain leaving the EU even vaguely on schedule. If it doesn’t pass, the Tories will cease to be a governing party in any meaningful sense. At cabinet this week, Michael Gove asked May how the government would whip the vote on a no-deal Brexit: would she instruct her ministers and MPs to vote for or against? She didn’t answer. The reasons why not take us to the heart of the current morass.

If she backs no deal, a slew of ministers (Greg Clark, Amber Rudd, David Gauke, and perhaps Philip Hammond and David Lidington too) would resign. If she abandoned no deal, she’d lose a score of ministers from the other wing of the party. But to offer a free vote on a matter of such importance would go against the whole basis for the existence of parliamentary parties. It would represent not only a collapse in the Prime Minister’s authority but in the coherence of the Conservative party.

The recriminations have already started. The cabinet ministers who threatened to resign if May didn’t offer this vote on no deal argue that they weren’t being disloyal. They claim they were trying to help her by pressuring their rivals, the European Research Group of Tory MPs headed by Jacob Rees-Mogg, to vote for May’s deal. Their case is that the ERG needed to see that it wasn’t going to get no deal by voting against May’s deal. They hope that the threat of a Brexit extension will scare these MPs into voting for the withdrawal agreement.

Any shift in the deadline, of course, increases the risk of Brexit being softened further — or of it not happening at all. If the UK requests an extension, the EU would determine how long it would last. Emmanuel Macron favours a lengthy extension, arguing that the longer the time span, the better the chance of the political dynamics in the UK changing to the EU’s advantage. With Corbyn now forced into backing a second referendum, you can see why the French reckon delay works in the EU’s favour.

When May met Leave-voting junior ministers on Tuesday night, she tried to reassure them that she wouldn’t simply agree to a lengthy extension. When one of them asked what would happen if Olly Robbins came back saying that a short extension was not negotiable, she shot back ‘I don’t just do what Olly Robbins tells me to.’ She said that a long extension ‘would be seen as a betrayal’ by the public.

Some of her allies argue that the EU would not propose a long extension, because if we stay beyond June, we’d have to take part in the European elections in May. But I understand that the civil service has been looking at ways of getting around this in a period of ‘continued uncertainty’ (their euphemism for a Brexit extension). One idea that has been mooted is of sending MPs or members of the House of Lords to the European Parliament to temporarily occupy the seats that would otherwise be filled by MEPs.

When I put this analysis to one cabinet minister, he said such a fix would violate the EU’s treaties and would not be tolerated. He insisted that means there could be no further delay beyond the end of June. This minister, a secretary of state, argues that this therefore sets up ‘a no deal vs deal vote with no alternative’ at the end of June, and that in those circumstances ‘the deal would definitely pass’ thanks to the Commons majority against no deal. But this assumes that Parliament wouldn’t already have seized control of the process by then in order to try to push through a softer Brexit.

Cabinet ministers also think that Corbyn’s decision to back another ‘public vote’ on Brexit makes it easier for Labour MPs to back May’s deal. One tells me that the ‘only option for Labour MPs who want Brexit is to vote for the deal’. A decent proportion of Labour MPs backing May’s deal would allow the Prime Minister to absorb a moderate-sized rebellion by the ERG, which is not showing any sign of folding. Speaking at a Spectator event on Tuesday, Jacob Rees-Mogg said he’d vote against her deal and for no deal — and that he’s relaxed about a short extension. One of those who has been acting as a conduit between No. 10 and the Brexiteer rebels tells me that ‘the thing that’ll get the ERG is not fear of an extension’ and that she’ll need to proffer ‘something that looks like a carrot, not a stick’.

The Prime Minister has one carrot to offer. Geoffrey Cox, the Attorney General, will not return from Brussels with anything as straightforward as a unilateral exit mechanism from the backstop, or a time limit on it. But hopes are mounting in government that Cox will get enough to change his written legal advice and declare that there is not a risk that the backstop will ‘endure indefinitely’, as he had previously warned. Tellingly, Cox told cabinet on Tuesday that he wouldn’t play a big role in the conversation they were having, as he was at a ‘sensitive point in the negotiations’. He left well before the end of the meeting.

If Cox does get something and it is enough to satisfy the DUP, who senior cabinet ministers believe are now looking for a deal, then things could move very fast. In these circumstances, influential figures in May’s inner circle would want to hold the meaningful vote as early as next week.

The Tories find themselves in an odd position right now: on the verge of either a prolonged period in power, or of collapse. If they can agree on Brexit, then the split on the left created by the Independent Group offers them an historic opportunity. The break-away MPs will not support an early general election, in which almost all of them would expect to lose their seats: they would need years to build up a party machine. Early polling suggests that this group is doing far more damage to Labour and the Lib Dems than to the Tories. This means that the Tories could win a comfortable majority at the next election on a reduced share of the vote.

But if there is no Brexit, the Tories will pay a dreadful electoral price. They would have failed a basic competence test. Voters would view the party with suspicion and that would compound the problem. It is hard to see how a catastrophic split on the right would not follow.

No deal would not be as disastrous for them. But it is hard to believe that it would not be damaging. At the very least, voters would notice the short-term logistical disruption that no deal would bring, and would ask — reasonably — why the government hadn’t done more to mitigate it. And no deal would also lead to more Tory MPs defecting to the Independent Group, along with a proportion of the party’s voters. It is worth remembering that at the last election, twice as many Remainers voted Tory as voted Lib Dem.

The Tory split over Europe has been long running. The issue has accounted for the careers of the last three Tory prime ministers. But Brexit is now stretching the Labour party to breaking point too. The eight Labour MPs who have defected to the Independent Group all did so, at least in part, because of their support for a second referendum. Corbyn is moving toward a ‘public vote’ on Brexit to try to avoid this split widening further.

Corbyn’s reluctance to back a second referendum isn’t just down to his own Benn-ite Euroscepticism. Of the 45 target seats in England and Wales that Labour need to win, 35 voted for Brexit. At the same time, of Labour’s 20 most vulnerable seats, 16 are Leave constituencies. A cynic might think that Corbyn is backing a ‘public vote’ now because he knows it would never be approved by the Commons. This way he can placate his pro-Remain MPs (and membership) while avoiding a reckoning with the Brexit voters to whom he needs to appeal.

It’s a risky strategy: as we have seen so many times since the referendum, things can change. If suddenly the numbers were there for a second referendum in parliament, it is hard to see how Corbyn could revoke his support for one. So there’s now a greater chance of a second referendum happening than there was a fortnight ago, when the idea looked pretty much dead.

Seldom has politics been less predictable. This is not just a hung parliament — it is a hung parliament in which neither the Prime Minister nor the leader of the opposition have control over their respective parties. Both May and Corbyn find themselves being stretched and contorted by rebel MPs, many of whom are sitting on their own front benches. Both leaders are desperately trying to get through the next few weeks, without thinking much beyond that. Neither of them can be sure if their party will make it to the summer intact. All of this makes politics, Brexit and the country’s future extra-ordinarily uncertain. It is hard to take back control when no one is in control.