Tuesday, December 11 essentially spells D-day for British Prime Minister Theresa May as MPs take their seats in the House of Commons to deliver their verdict on her government's Brexit deal.
After five days of debate, they will vote on both the withdrawal agreement, a 599-page-long legally-binding document that sets out how the UK leaves the European Union, and the future political framework — a set of ambitions for a European Union (EU)-UK trade deal.
Adding pressure to the mix, MPs on Tuesday also backed calls for the Commons to have a direct say in what happens if May's Brexit deal is rejected.
If the deal is voted down, the government will have 21 days to return to the Commons and set out what it plans to do next.
What are the possible outcomes of the vote?
If MPs accept the deal, Britain is sure to leave the EU on March 29, 2019, but if they reject it, the resulting whirlwind of political activity would be on a scale unrivalled in the UK for decades.
"What is possible is that the withdrawal treaty is defeated and that, of course, is what most people expect," Pieter Cleppe, Head of Open Europe's Brussels office, told Euronews.
Until now, May has enjoyed a majority of 13 in the House of Commons, with the support of the Democratic Unionist Party (DUP), but the Northern Irish party has vowed to vote down the deal.
Labour, the Scottish National Party and Liberal Democrats have all come out against the deal and around 100 MPs have criticized the agreement.
The second question is the degree to which the deal is defeated: "Will it be 10, 50 or 100 MPs short, we don't know," said Cleppe.
A vote of no-confidence
Labour has vowed to call a motion of no confidence in the government if the deal is rejected and, if backed by a majority of MPs, this could force a general election.
Cleppe thinks this is most likely to happen but, given that May enjoys a majority in parliament, "this is likely to fail".
Broadly speaking, if a general election is called, which results in a change of leadership, anything from a second Brexit referendum to a no deal could happen.
In the event of either a second referendum or general election, the EU could agree to extend Article 50 beyond March 2019.
Amid all the confusion, a disorderly no-deal cannot be ruled out.
On the question of a second Brexit referendum in the case of a new leader, Cleppe said: "Of course, it's possible, anything is possible, but we need a whole lot of conditions fulfilled first."
The Labour Party needs to be in favour of that, which is still ambiguous.
Another deal could also be on the cards like a managed no deal, on World Trade Organisation terms, a "Norway Plus" deal in which the UK would remain part of the EU's single market and customs union or a super-Canada a trade deal.
May resigns or her own party kicks her out
May could resign if she loses Tuesday's vote or the Conservative Party could also call a vote of no confidence in her as party leader — the most likely to do this would be hardcore Eurosceptic MPs.
To do this, 48 Conservative MPs would need to write to the chairman of the 1922 Committee.
If May is no longer leader, there will most likely be an interim leader like her de facto deputy David Lidington.
Following this, the contest to find a permanent replacement will ensue, which, even if fast-tracked, could take over a month. Everyone from Boris Johnson to Amber Rudd likely to enter the fray.
May stays in post
If May survives these hurdles, she could seek a second vote on her deal.
She might also look for some tweaks to the Brexit package, but she'd need Brussels' and finally the House of Commons' agreement.
Logically, Cleppe thinks Theresa May will try to change the political declaration at the December 13-14 summit in Brussels.
This would mean the EU could "save face" as it could claim it hadn't renegotiated the withdrawal agreement but simply "tinkered with the non-binding political declaration".
May could also use this as a way to convince certain pro-EU Labour MPs to back the deal, he added.
"These people would have to make up their minds — do they still believe in a second referendum, or do they believe its a lost cause," Cleppe said.