13/01/2019 06:00 GMT | Updated 15/01/2019 17:48 GMT

This Is How Tuesday's Crunch Brexit Vote Will Play Out - And What Happens If May Loses

You'd be hard pushed to miss the fact it's happening - but how does it actually work?

It’s just hours until MPs finally cast their vote on Theresa May’s Brexit deal, determining the direction the UK will take as it leaves the EU.

Will the threat of no-deal scare enough MPs into backing Theresa May and her controversial backstop? Or will the European Research Group – a collection of ardent Brexiteers passionately opposed to the PM’s deal – be able to gather up enough support to topple the plan?

One way or another, it’s what we’re all going to be talking about. But how will the week actually pan out?

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The Week So Far... 

It was hardly a great start to the week for May, with a letter from EU leaders Donald Tusk and Jean Claude Juncker to the PM intended to reassure Brits about the controversial backstop agreement going down like a tonne of bricks among Tory MPs. 

With the backstop a key point of contention among many MPs on May’s own benches, the pair’s admission that they were “not in a position to agree to anything that changes or is inconsistent with the Withdrawal Agreement”, was not received well. 

“We have to be clear this is not acceptable,” Tory MP Damian Collins wrote on Twitter. “We must have an independent means of ending the backstop.” 

Meanwhile, Conservative Ben Bradley branded the letter “just fluff”. 

But the prime minister’s run of ‘misfortune’ did not end there. Just a day before the crunch vote on her Brexit deal, one of her own whips – the people tasked with getting Tory MPs to vote in line with the government – resigned. 

In his resignation letter, Gareth Johnson said he had struggled to bring together his duties as a whip with his personal feelings on May’s proposal on how to leave the EU. 

“I have concluded that I cannot, in all conscience, support the government’s position when it is clear this deal would be detrimental to our nation’s interests,” the Dartford MP wrote.  

Tuesday And Beyond... 

After a gruelling five days of parliamentary debate on May’s Brexit deal, Tuesday evening will see MPs finally given the chance to decide whether to back the PM’s proposal on how the UK should leave the EU.

The so-called ‘meaningful vote’ comes a month later than originally expected after it was shelved by May back in December, who admitted at the time that her deal would have been “rejected by a significant margin”.

So the moment that MPs file into the Commons’ division lobbies will be a huge one for the PM – has she done enough to convince MPs, including those in her own party, to back the Chequers deal?

It won’t take long to find out. As little as 15 minutes later – after MPs have had their names recorded and counted by Commons officials – Speaker John Bercow will announce the result.

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Bercow will announce the results of the meaningful vote 

Here’s where things get really interesting. If May has remarkably managed to whip up a majority for her deal, the UK will leave the EU under the terms negotiated by the Prime Minister and her team – including the divisive Irish border backstop. (As long as it is passed by the European Parliament and Council.)

If she hasn’t… things get a bit more complicated.

Last week, the government suffered a significant defeat in the Commons after rebel Tory MPs joined forces with Labour to push through an amendment which means May will have just three sitting days to come back to the House with a new Brexit plan, instead of the previously agreed 21.

The amendment – put forward by Tory MP Dominic Grieve in a bid to avoid a no-deal Brexit – will give MPs the chance to vote on alternative Brexit plans – including a second referendum, a ‘managed’ no-deal or a ‘Norway-plus’ option.

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If a new deal is agreed by parliament, the government could go back to Brussels in an attempt to renegotiate a deal. But, given the fact that Brexit day – March 29 – is just weeks away, this would probably lead to an extension of Article 50.

Finally, if May loses the Brexit vote, Labour could trigger a no-confidence vote in the government, with Jeremy Corbyn announcing on Thursday it would trigger such a motion “at the moment we judge it to have the best chance of success”.

If MPs determine they have no confidence in the government, this in turn could trigger a general election.

Buckle in folks – it’s going to be a hell of a week.