It's the day of reckoning in Westminster, as MPs prepare to vote on whether to accept or reject Theresa May's Brexit deal.

In a day likely to be filled with political jargon, positioning and spin, Sky News takes you clearly through how the run-up to the "meaningful vote" will unfold.

:: May's sit-down with her cabinet from around 9am

Well before MPs arrived in parliament for the afternoon debate, Mrs May chaired the weekly meeting of her cabinet.

All of her most senior ministers were there to discuss issues of the day.


Image: Jeremy Hunt arriving at the cabinet meeting this morning

Brexit - and particularly planning for a "no-deal" divorce from the EU - has featured heavily in recent weeks.

:: Brexit debate in the Commons this afternoon

Image: John Bercow will pick amendments for debate. Pic: UK Parliament/Mark Duffy

Trying to say with certainty when anything is happening in parliament is almost harder than negotiating the backstop.

But the Commons session began at 11.30am, with the Brexit debate starting around 12.45pm.

MPs who have still not had a chance to reveal how they plan to vote and give their reasons why will finally get that chance.

The debate is due to wrap up at 7pm.

:: The question of amendments

Image: There is no limit on how many amendments could be considered

Before voting on the final deal, MPs will vote on a series of amendments to it.

At least 13 were tabled but the Speaker, John Bercow, has only given permission for four of them.

They come from Jeremy Corbyn; the SNP's Ian Blackford and Plaid Cymru's Liz Saville Roberts; Tory Brexiteers Sir Edward Leigh and Sir John Hayes; and Tory MP John Baron.

:: The meaningful vote - around 8pm

Image: Brexit is due to happen on 29 March by default

Exactly when the vote will be depends on how many amendments are voted on.

Each one will take around 15 minutes, meaning the vote is expected to take place around 8pm.

:: Is there any way the vote could be pulled?

Image: Mrs May faces huge opposition from her own MPs - Brexiteers and Remainers

It's now very unlikely.

Senior Labour MP Hilary Benn confirmed on Tuesday morning that he was withdrawing his amendment to reject both the PM's deal and a no-deal Brexit.

It could have avoided the key vote on the deal going ahead had it been approved.

But Mr Benn was under pressure from colleagues to ditch the amendment to make sure Mrs May faced the vote.

:: How will the vote happen?

Image: MPs will walk through one of two lobbies to vote on the deal

MPs will rise from the green benches in the Commons chamber and exit into one of two corridors.

These are the "aye" and "no" lobbies.

MPs voting for the deal will file down the aye lobby, which runs behind the side of the house where members of the government sit.

MPs voting against the deal will head into the no lobby, which runs behind the opposition side.

They will all give their names to a clerk at the end of the corridor, and register their name with two "tellers" - nominated by the two sides to declare the result.

After 15 minutes, the voting lobby doors will be closed.

MPs will re-take their seats in the chamber, as the tellers line up in front of the Speaker to declare the result.

You can tell before they open their mouths which side has won, as the victors will be standing on the right.

Find out how each MP has declared they will vote here.

:: What happens if May wins?

Image: Theresa May will close the debate on Tuesday

If the prime minister has managed to convert the more than 100 Conservative MPs who are planning to vote down the deal, it will be written into law.

That means the UK will leave the EU on 29 March with an agreement.

:: What happens if she loses?

Image: One amendment calls for another referendum on the Brexit deal

Under an amendment passed last week, if Mrs May loses she has just three sitting days of parliament to return and present her next steps - or plan B.

The government has announced MPs will not be sitting on Friday, so that makes the prime minister's deadline the following Monday - 21 January.

Everything else is in the hands of the amendments being tabled tonight.

One calls for the Northern Ireland backstop to only be temporary, another for the UK to get power to end the arrangement without permission from the EU.

:: Could the government face a no-confidence vote?

Mr Corbyn could also use the defeat to strike and launch a vote of "no-confidence" in the government to force a general election.

There is speculation in Westminster this could come immediately after the result is announced, with a point of order being raised in the House of Commons.

The vote itself could follow as soon as Wednesday, with reports Labour is targeting the slot after Prime Minister's Questions.

Mrs May's confidence and supply partners the DUP have said they will support her in such a vote, which if every Conservative MP does as well should keep her job safe.

However, if she loses, all bets are off.

There is then a period of 14 days in which a new government can be formed, before a general election is triggered.

Mrs May could attempt to cling on and form a new administration, or she may decide it is time to go and hand the reins over to someone else.



A new Conservative leader would then have the chance to form a government, while Labour could have a go themselves.



The new government is confirmed in office through passing the following resolution in the Commons: "That this House has confidence in Her Majesty's Government".

:: Follow and watch the Brexit vote live with a special programme on Sky News from 6-10pm tonight.