Boris Johnson will be hoping to bring back a new Brexit deal from the all-important EU summit starting in Brussels on Thursday.
But the outcome of the two-day meeting of Europe’s leaders is anything but certain for the Prime Minister.
Here the PA news agency looks at three key scenarios that could take place and the eventualities that could follow.
What seemed practically impossible a week ago may just happen and the PM could get a deal signed off on by the EU leaders.
Polish the trumpets, roll out the red carpet and butter the cucumber sandwiches: Brexit is coming. Not quite…
Even if a legal text is backed all round in Brussels, Mr Johnson has still got to get it approved by a Parliament that has so far proved anything but compliant.
MPs rejected Theresa May’s deal three times and they have dealt Mr Johnson a series of humiliating blows, even tying his hands to prevent a no-deal exit.
But while the biggest change to the parliamentary arithmetic is the PM expelling 21 Tories who rebelled against him, there has been a change in mood.
The DUP, which scuppered Mrs May’s deal at every turn, is in close contact with the PM and has signalled it could be approving.
Not only does Mr Johnson need the backing of Arlene Foster’s 10 MPs for the numbers, they are also highly influential for the hardline band of Tory Brexiteers, the European Research Group (ERG).
Self-proclaimed “Brexit hardman” Steve Baker, who chairs the group, has signalled he could support the deal.
A group of Labour MPs may also back an agreement out of a fear that a no-deal exit would be the alternative.
This could all be tested during an extraordinary sitting of Parliament on Saturday, the first time this has happened in 37 years.
Any request for such a sitting would need to be approved by MPs on Thursday.
But would Parliament approving a deal stop all the talk of Brexit? Not in the slightest: This is where the real hard work begins.
With the Withdrawal Agreement and Political Declaration in place, negotiations on the future relationship between the UK and the bloc could begin with the start of the transition period.
– No deal
If Mr Johnson comes back empty handed, he returns to a conundrum.
He is compelled by the Benn Act forced through by MPs opposed to a no deal to ask for an Article 50 extension if Parliament does not vote for an agreement by Saturday.
But he has repeatedly insisted he would not request a delay from Brussels under his “do or die” commitment to deliver Brexit by the current October 31 deadline.
Brexit Secretary Stephen Barclay confirmed on Wednesday that the PM would send the desired letter, though scepticism remains.
Any other move would lead to an almighty clash with MPs and a likely court case with allegations he has broken the law.
Is he bluffing, does he have a loophole tucked up his sleeve or will he resign to let someone else take the top job and ask for the delay? The answer is not yet clear.
But, if the Saturday showdown gets the go-ahead, MPs could be asked about another way forward.
Or they could be taunted by Mr Johnson in his latest “people versus Parliament” posturing as he campaigns for a general election he is yet to get the Commons to approve.
Any request for an extension, specified in the Benn Act as to the end of January, would then need the backing of all 27 remaining EU nations.
– Something in between
An alternative scenario would see the UK and the EU achieve a “political agreement” on a deal – one where there is no legal treaty text but where the principles are agreed.
This would not satisfy the Benn Act and the PM would have to request an extension, but this may be enough to win over some of his critics and could play sufficiently well with his voters.
He could essentially say it is not a real delay, just one to dot the i’s and cross the t’s so he can deliver Brexit as he always promised.
Irish Taoiseach Leo Varadkar was reported to have raised this prospect of a “technical extension” during a phone call with the PM, and he has also suggested a second EU summit could be held this month.
Mr Johnson may still want to stage a Commons vote on this in order to judge the numbers and demonstrate to the EU that the official deal could get through.
But, providing the lawyers do not tear up the agreement, MPs could still reject it.
It has been suggested that the extension needed under this scenario could be shorter than what is demanded by the Benn Act, perhaps until January 1.
Either way, a further delay to Brexit would be inevitable.
It will then be up to the voters – and the PM’s Conservative colleagues – to decide what they make of how he lived up to his “do or die” commitment to deliver Brexit by October 31.