A deal for the UK leaving the EU could be approved tonight - if MPs agree, and that's the big question.
Here's a quick (as it can be) round up of the key facts and times
Theresa May will return to the House of Commons for a second meaningful vote on an amended deal tonight, scheduled to take place at 7pm.
What happens if it passes?
If the vote passes, MPs would then move on to the legislation required to implement the deal. Ideally, the government would like this to be in place by 29 March - the planned date for Brexit - but it is possible a short delay would be needed to finalise arrangements.
What happens if it doesn't?
Theresa May has promised if the deal fails, there will be a vote on leaving the EU with no deal tomorrow. There appears to be no majority for a no-deal Brexit, so if that were voted down as expected, a vote on delaying Brexit.
If those fail as well, the default position is for a no-deal Brexit.
What happens if MPs back the delay?
Theresa May would request an extension to Article 50 from the EU. If they agreed, Brexit would be postponed. Theresa May has said this should be for no longer than three months.
The big question is what happens next. It could lead to no deal at a later date if no other outcomes can be found.
There could be another vote on the Prime Minister's deal.
If not, a major renegotiation would be needed with the EU, not just tweaks to the current offer on the table.
There are also concerns around the length of the delay. Would the three months mentioned by Theresa May be long enough? European Elections are due to take place this summer. Would the UK need to put up MEP candidates? The EU would wish to avoid the problems this threw up.
A significant delay is also likely to anger Brexit voters who are concerned the Government and/or Parliament is trying to wriggle out of their democratic decision.
What are the new securities Theresa May brought back from negotiations last night?
Theresa May and Jean-Claude Juncker have agreed three new documents which the Prime Minister believes will provide MPs with the legally-binding reassurances they require to approve the Withdrawal Agreement and Political Declaration on the future EU/UK relationship agreed in November.
MPs will be asked to approve the Agreement and Declaration, along with the three new documents, in the House of Commons on Tuesday.
If the package passes the Commons, leaders of the 27 remaining EU states will be asked to endorse the new documents at a scheduled European Council summit in Brussels on March 21-22, before the final step of ratification by the European Parliament.
The new documents are:
The instrument relating to the Withdrawal Agreement:
This four-page document largely repeats assurances in letters exchanged on January 14 between Mrs May and European Commission president Mr Juncker and European Council president Donald Tusk, setting out both sides' intention that the backstop arrangements contained in the Withdrawal Agreement and intended to keep the Irish border open afterBrexit should not be permanent.
Crucially, the instrument explicitly states that it represents a "clear and unambiguous statement by both parties" of what they have agreed and therefore "constitutes a document of reference that will have to be made use of" if any issue arises in relation to the implementation of the Withdrawal Agreement.
"To this effect, it has legal force and a binding character," states the instrument.
It states that "the parties do not wish the backstop solution in the Protocol on Ireland/Northern Ireland to become applicable, that were it to do so it would represent a suboptimal trading arrangement for both sides and that both parties are therefore determined to replace the backstop solution for Northern Ireland by a subsequent agreement that would ensure, on a permanent footing, the absence of a hard border on the island of Ireland".
It states that this eventual permanent arrangement must respect the integrity of the EU's internal market and the territorial integrity of the UK.
And it promises regular reviews of the arrangements for the island of Ireland to allow the two sides to consider whether they are still needed or "could cease to apply in whole or in part".
The instrument says that after the end of the transition period in December 2020, any differences over the arrangements will be dealt with under the dispute settlement mechanism set out in the WA.
The unilateral declaration by the UK Government:
This three-paragraph statement sets out the UK Government's position that the objective of the Withdrawal Agreement is not "to establish a permanent relationship" between the EU and UK, and that the backstop provisions are therefore "intended to apply temporarily".
The declaration states that the UK Government's understanding is that nothing in the Withdrawal Agreement would prevent it from taking steps to end the backstop arrangements if it proves impossible to conclude a broader trade deal with the EU.
It states that this is subject to the condition that the UK will uphold its obligations under the 1998 Good Friday Agreement and will avoid the creation of a hard border.
The joint statement supplementing the Political Declaration:
This two-page document sets out additional measures to "enhance and expedite" the process of negotiating a future trade and security relationship between the UK and EU.
It restates the "clear and important link" between the Withdrawal Agreement and Political Declaration as "part of the same negotiated package".
And it says that both sides have the "shared ambition" of concluding an agreement on the future relationship by the end of the transition period in December 2020.
Crucially, it states that the two sides will set up a "specific negotiating track" to examine technological solutions - referred to as "alternative arrangements" - to keep the Irish border open and replace the proposed backstop "in whole or in part". Progress on this work will be subject to regular review.
Negotiations will begin immediately after the UK's withdrawal and talks on different strands of the relationship will proceed in parallel, promises the document. Once the negotiations are complete, the European Commission will be ready to apply the new deal on a provisional basis, rather than waiting for the ratification of national and regional parliaments across Europe.
The joint statement notes Mrs May's pledge that the UK will not "regress" on social, employment and environmental standards after departure and that MPs will be given a chance to vote on matching any future changes to EU regimes.