So what happens next week?

MPs return to parliament from their summer recess next Tuesday. The Commons is due to rise again during the annual autumn party conference season, meaning there is only a window of a few weeks in September and October for MPs to halt a no-deal Brexit.

The PM has emphasised his priority is to a strike deal with Brussels that is different from the withdrawal agreement secured by Theresa May, with the future of the Irish border the over-riding concern.

To that end, Johnson is set to send his EU “sherpa” – his Europe adviser David Frost – for talks with Brussels officials on Wednesday to discuss the so-called backstop further. 

But his “do or die” threat to leave on Halloween appears sincere. The prime minister warned Brussels on Tuesday night that no-deal would happen unless the Irish backstop was “abolished”.

Is there a plan to stop no-deal?

Nothing concrete has emerged yet.

Opposition leaders on Tuesday agreed to prioritise a legislative approach, suggesting Jeremy Corbyn will not immediately push ahead with a move to oust Johnson in a vote of no confidence – the plan that has grabbed most headlines over the summer.

After Corbyn met with Lib Dem leader Jo Swinson and the SNP’s Westminster leader Ian Blackford, among other senior MPs, the precise plan was being kept under wraps. It is thought this is largely because the government could try to scupper it with counter moves using parliamentary procedure.

Johnson himself has repeatedly refused to rule out suspending parliament – known as proroguing – to undermine attempts to block his route to an October 31 exit.

But some kind of emergency motion could be tabled at some stage next week, and Commons Speaker John Bercow is set to play a crucial role if it does.

MPs could use Standing Order 24 of parliament’s rules, where they apply to the Speaker for an emergency debate on a matter requiring urgent consideration. Though these debates traditionally consider motions in “neutral terms”, which means they cannot compel government action and are not legally binding, Bercow could allow MPs to amend it – potentially giving them the chance to vote to delay Brexit.

On Tuesday, the Westminster leaders were asked about a last-minute High Court legal injunction to block Johnson from proroguing parliament to force through a no-deal Brexit. It is unclear whether any injunction could bind the UK’s prime minister. 

So no vote of no confidence?

Not in the first instance. A vote of no confidence has been floated throughout the summer, with opposition MPs increasingly vocal about the device, but critics have warned the process would not necessarily stop no deal.

In any case, Corbyn’s proposition that a he would be the ‘caretaker manager’ in an emergency government of national unity received a cool reception from the Lib Dems. MPs have suggested Ken Clarke or Harriet Harman should assume the role instead.

Even if the vote carried, Johnson could refuse to follow constitutional convention to resign.

What about the general election speculation?

An almost relentless policy blitz by Johnson since becoming PM has prompted  speculation that his team favour going to the polls to secure a mandate for his strategy. 

There has also been repeated calls from opposition MPs to go back to voters to secure a change of government. Defeat could stop no-deal.

Received wisdom suggests there is little time in reality to hold a general election before October 31, but Chancellor Sajid Javid sparked fresh snap election speculation with a plan to boost spending next week that will be presented as drawing a line under austerity.

And a second referendum? 

This option failed to secure a parliamentary majority during the indicative votes process earlier this year.

Such a move could only happen with government support through legislation and the government’s position is to pursue Brexit and leave the EU on October 31 following the referendum decision in 2016.

Revoking Article 50 and remaining in the EU, although backed by some MPs, has failed to win enough parliamentary support and is opposed by the government.

What about the Tory rebels?

Probably the biggest stumbling block at the moment.

Despite Johnson’s majority of just one, Tory rebels would still be needed to make any of the plans work – especially a vote of no confidence – given the core of pro-Brexit Labour MPs. But Conservative MPs were conspicuous by their absence from a cross-party event to mark around 160 MPs signing a declaration to support doing “whatever is necessary” to stop a no-deal Brexit. 

A band of Tory MPs, led by ex-chancellor Philip Hammond, have made clear their unease at a hard Brexit, but a guarantee they would move against a Conservative government is far from assured. Their loyalty has also been tested after Germany’s Angela Merkel offering Johnson a 30-day timeframe to find a way out of the stalemate.

Former Tory minister Anna Soubry – now an independent – hit out at the cowardice of Conservatives who privately oppose a no-deal Brexit but refuse to stop Johnson pursuing one.

Tory party enforcers will almost certainly target Tory wobblers next week, telling them that Johnson really is playing for a deal with Brussels, and urging them to keep their powder dry until all options have been exhausted – likely by the EU summit on October 17. While that might convince some Tories, others will see it as too late to test whether the PM’s hands can be tied.