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It’s the week when all could change, or nothing could. When we find out what the next few weeks, months and years could hold – or not. Yes, it’s Brexit’s crunchiest crunch time yet. Maybe. With barely a fortnight to go, we still have no clue.

After making no discernible progress in Brussels on obtaining a unilateral exit mechanism to the Irish backstop, Theresa May promised a second “meaningful vote” would go ahead on Tuesday after being told she would lose parliament’s confidence if it didn’t.

After a last-minute dash to Strasbourg it emerged that assorted assurances – a legal add-on to the withdrawal agreement, some additional language in the political declaration – had been found.

Quick guide What is the Brexit ‘backstop’? Show Hide What is the original ‘backstop’ in the withdrawal agreement? Variously described as an insurance policy or safety net, the backstop is a device in the withdrawal agreement intended to ensure that there will not be a hard border between Northern Ireland and the Republic of Ireland, even if no formal deal can be reached on trade and security arrangements. It would mean that if there were no workable agreement on such matters, Northern Ireland would stay in the customs union and much of the single market, guaranteeing a friction-free border with the Republic. This would keep the Good Friday agreement intact. Both the UK and EU signed up to the basic idea in December 2017 as part of the initial Brexit deal, but there have been disagreements since on how it would work. The DUP have objected to it, as it potentially treats Northern Ireland differently from the rest of the UK, creating a customs divide in the Irish Sea, which is anathema to the unionist party. Hardline Tory Eurosceptics also object to it, as they perceive it to be a trap that could potentially lock the UK into the EU’s customs union permanently if the UK & EU cannot seal a free trade agreement. That would prevent the UK from doing its own free trade deals with nations outside the bloc. What was added to May’s withdrawal agreement? Joint interpretative instrument

A legal add-on to the withdrawal agreement was given to Theresa May in January 2019 to try to get her deal through the UK parliament. It gives legal force to a letter from Jean-Claude Juncker and Donald Tusk, the presidents of the commission and council. This stated the EU’s intention to negotiate an alternative to the backstop so it would not be triggered, or, if it was triggered, to get out of it as quickly as possible. Unilateral statement from the UK This set out the British position that, if the backstop were to become permanent and talks on an alternative were going nowhere, the UK believes it would be able to exit the arrangement. Additional language in political declaration This emphasises the urgency felt on both sides to negotiate an alternative to the backstop, and flesh out what a technological fix would look like. However, it failed to persuade the attorney general, Geoffrey Cox, who said that while it ‘reduces the risk’ of the UK being trapped in a backstop indefinitely, it does not remove it. What happens next? Boris Johnson declared the Northern Ireland backstop ‘dead’ during his leadership campaign, and promised to throw it out of any deal he renegotiated with the EU. The EU has repeatedly stated that it will not reopen the withdrawal agreement for renegotiation. Daniel Boffey, Martin Belam and Peter Walker

These could, in the government’s view, amount to the “legally binding changes” it sought, with a legal commitment to finding “alternative arrangements” to the backstop by December 2020. That, in turn, might allow the attorney general, Geoffrey Cox, to soften his view that the UK risked being permanently trapped in the backstop.

All this might persuade some moderates. But this is, essentially, interpretation of what already exists. The withdrawal agreement itself has not changed, and whether hardline Brexiters in the Tory European Research Group – and the Democratic Unionist party – will now roll over is moot.

Should the deal be voted down once more (Eurosceptics warned during the week that even if May offered to quit in exchange for their votes, it would not pass as it stood), some Tories are openly muttering that the PM’s days are numbered.

After a week in which Cox blustered to no great effect on the backstop (annoying Brussels palpably in the process), Michel Barnier, the EU’s chief negotiator, confirmed (again) there could be no substantive changes to the withdrawal agreement – but ended up offering to fudge things a bit around the edges.

In a speech in leave-voting Grimsby, May urged everyone – MPs and the EU alike – to “get it done”, warning defeat for her deal would mean uncertainty, delay and the possibility of Brexit being either watered down or even reversed.

What next

It all depends, obviously.

So the government’s efforts to persuade the EU27 to provide “legally binding guarantees” on the backstop eventually delivered something. All will hang on whether the Brexiters and DUP are willing to compromise. A defeat is still very possible – if by no means certain.

A narrow defeat (fewer, say, than say 50 votes) might tempt her May to try a third meaningful vote. Before that, though, she faces two further votes this week, on excluding no deal, and delaying Brexit – and possible ministerial resignations.

But a defeat by more than 50 votes could put the prime minister under intense pressure from remainers to let parliament decide on the next steps – by which they mean seeking a softer Brexit. In those circumstances, she could yet decide to go.

If there is to be an extension to article 50 (which even if May’s deal passes now appears almost inevitable, if only by a few weeks, to get the legislation through parliament), the EU27 will need to approve it at their meeting on 20 and 21 March; if they don’t there would a very high risk of the UK crashing out without a deal.

If the deal is not agreed, there will be a fight over how long any extension should be, with leavers arguing for it to be as short as possible (ending before the new European parliament starts sitting in July) and remainers preferring a longer period to allow time for alternative options, including a referendum.

Best of the rest

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In the Guardian, Martin Kettle says Britain has cut itself adrift from Europe, and he fears it may sink – we have yet to grasp the scale and complexity of the next phase of Brexit talks:

The future political and economic relationship with the EU, most of which is airbrushed in the deal’s political declaration, holds the key to the country we will all live in for the next decade and more. That negotiation hasn’t even begun. What sort of relationship do we want to have with the EU in the future? The failure to answer this question remains bound up in Conservative party politics. May is frightened of giving the true answers – hug the EU close to ensure a Brexit that will work for as many people as possible. Instead, she has fed the belief that real divergence with the EU can now begin … But the next phase will be much more difficult and wide-ranging than the article 50 phase.

And Matthew d’Ancona argues that politicians’ character can be judged in this vital Brexit week – but they are putting blatant self-interest ahead of the Brexit vote:

On Wednesday, the Commons will vote on “no deal”, and will almost certainly mandate the government to rule it out. This, in turn, will force May to do what she has most dreaded, which is to give parliament the chance to seek an extension of article 50. And it is at this point that the character of our political class should truly be judged. Will it seek a meaningless three-month deferral, as the PM hopes, or – in dialogue with the EU – ask for a longer period, in which parliament can pause, draw breath and, if it sees sense, give the voters a chance to break the impasse? There are no risk-free options now, no steady as she goes, old-fashioned British compromise. The whole issue has to be reframed, re-energised and rescued from its present captivity. Jeremy Hunt has said the deal’s failure this week would risk “Brexit paralysis”. But where do he and his colleagues imagine we are right now?

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An unnamed senior Tory, via ITV’s Robert Peston, sums up where things stand: