Parliament has not yet returned from its summer break but we are already in a bitter constitutional battle, with the Prime Minister pitted against the Speaker of the House of Commons and the opposition parties. Boris Johnson’s decision to prorogue parliament is a deliberate attempt to raise the stakes. He wants to deny time to any effort by MPs to pass a law forcing him to request a Brexit extension. His message to them: bring me down or let me get on with Brexit.

When parliament returns on Tuesday for a two-week session, MPs will have to decide how to respond to Johnson’s move. Opposition MPs had previously agreed to try to use legislative means to compel the government to seek an extension, as they did before the last Brexit deadline with Yvette Cooper’s bill. But Johnson’s actions show that such an effect is unlikely to succeed; he won’t play by the same rules that Theresa May did.

If proroguing isn’t enough to stop these legislative sallies, then the government has other devices to neuter them. As a new Policy Exchange paper from the Oxford law professor Richard Ekins shows, making these efforts watertight is more difficult than MPs might think. Just look at how Boris Johnson has got around the bar on prorogation that Dominic Grieve’s amendments to the Northern Ireland executive formation bill supposedly created.

What would the Commons do if Boris Johnson fulfilled the legal requirement to request an extension but did so in a manner that made it almost certain that the EU would reject it? This would not be hard for him; he would just have to promise to be as disruptive a member as possible. In these circumstances, at least one of the EU 27 would veto the request.

Or Johnson could simply say that he was not going to do it and that if parliament wants to ask for an extension, then it needs to replace him as prime minister. The only way that MPs could do that is through a no confidence vote. We know that Boris Johnson would not resign on losing such a vote but would instead seek to call an election for after Britain left the EU. Thwarting this approach would require an alternative government that could clearly command the support of the Commons. But this runs into a problem: there aren’t many Tory MPs who would want to put Jeremy Corbyn in No. 10, while the Liberal Democrats know that looking like Corbyn’s enablers would be problematic for them. At the same time, it isn’t in Corbyn’s interests to allow anyone else to become prime minister. As one cabinet minister argues, a legislative attempt to block no deal only works if you’re also prepared to change the government  —  but doing that makes an election and  —  because of the Fixed Term Parliament Act  —  a 31 October departure much more likely.

Another challenge for those who want parliament to move as soon as it returns in September is that a deal still seems possible. Boris Johnson is adamant that his preference is to leave with an agreement. He has told MPs that the number one legislative priority for his Queen’s Speech will be a new Brexit deal, if one can be agreed.

After the G7 summit in Biarritz, this seems slightly more likely than it did previously. The EU’s position that the withdrawal agreement cannot be reopened does not appear as set in stone as it once did, and the talks between the UK government and the EU are becoming more serious.

There is, of course, a distance to go from reopening the withdrawal agreement to Boris Johnson’s demand that the ‘undemocratic backstop’ be scrapped. I understand that the Downing Street view is that even an agriculture-only Northern Ireland backstop must have some form of exit mechanism.

But the suggestion that Johnson’s approach might just be working will make some Tory MPs inclined to give him more time. They’ll be loth to join in any effort to bring down the government next week, and will take the view that the time to act is nearer the Brexit deadline when it is clear whether Johnson has succeeded in getting a deal or not.

This does not leave much time. Boris Johnson’s first EU Council meeting is not until 17 October, a mere fortnight away from the date for the UK’s departure. This means that it will be late October before anyone can say with certainty that there will definitely be no deal, unless there is an extension.

No. 10 has been pointing out to Tory MPs that Angela Merkel told Boris Johnson at their meeting last week that if a deal was going to be done, it would be late in the day — and not before the October EU Council meeting. The argument is that MPs must let Boris Johnson go to that meeting with the ability to walk away from the table. At the same time, No. 10 is warning them that if they legislate to block no deal they won’t stop it but guarantee it. Why? Because that would lead to an election that wouldn’t take place until after 31 October.

Even those in No. 10 who were previously sceptical about a deal ever being reached are slightly more optimistic now. But it is worth remembering that the government’s Brexit planning committees are still operating on the assumption that no deal will happen. A deal would also present political challenges to the government. Right now, the cabinet is surprisingly united. But a genuine offer from the EU would undermine that. A large chunk of ministers would be inclined to take a deal that severely limited the backstop even if that would require Labour votes to get it through the Commons. Others, though, would be more concerned about preserving Tory unity and denying the Brexit party any political space. Interestingly, those ministers who are keenest on a deal feel that Boris Johnson is moving their way. Set against this is the fact that there is barely any time to get a new deal onto the statute book before 31 October.

The summer has been Boris Johnson’s honeymoon. But he will spend this autumn fighting for his premiership, his political life and his vision for Brexit Britain. The stakes could not be higher for him, his party or his country.