THE Hallowe'en Brexit day is fast approaching but the stakes are high and the drama is not over yet.

First up is what is expected to be a historic House of Commons showdown today.

It has been dubbed "Super Saturday" but what will actually happen and what will it mean for everyone?

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What is "Super Saturday" and why does it matter?

The House of Commons usually sits from Monday to Thursday, and on the occasional Friday. But today, Saturday, there will be an extraordinary sitting of Parliament - the first on a weekend since April 1982 - to discuss Boris Johnson's new Brexit deal.

On Thursday, MPs approved a motion to hold the first weekend sitting of Parliament since the Falklands conflict.

If Parliament does not vote for the agreement on Saturday, Mr Johnson faces an almighty clash over whether he will request a further Brexit delay from Brussels as he is compelled to under the Benn Act.

What will take place today?

The Commons will sit from 9.30am and the Lords will sit from 10am. The first order of business will be a statement from the prime minister to update the house after the EU Council summit.

After Mr Johnson's statement, the government is expected to move its motion seeking MPs' approval for a Brexit deal.

MPs have been able to table amendments since Thursday night, and speaker John Bercow can select as many amendments as he wants, with votes taking place on those before the vote on the Government motion.

The debate on the motion can run until any time on Saturday, and despite what people thought - and perhaps hoped - there is not a 2.30pm cut-off time.

But there should be indications of the sitting length on the day.

Will MPs vote for the prime minister's deal?

The vote could come down to the tightest of margins but it is understood the prime minister is working hard to win over MPs.

DUP MP Sammy Wilson has said his party would continue to hold firm and will vote against the deal on offer, while Nicola Sturgeon has ruled out her MPs in the SNP backing the deal.

Jeremy Corbyn was quick to dismiss the agreement, and said Labour could not support the deal. But, this is where things get interesting.

Attention has turned to the Labour Party's own psychodrama, with focus on what MPs in Leave-voting seats will opt to do.

The Daily Telegraph reported that between 10 and 15 Labour MPs are prepared to back the deal to avoid a no-deal scenario.

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Is it as simple as one yes or no vote?

No. MPs amended the Saturday sitting motion by approving a proposal tabled by former Tory minister Sir Oliver Letwin, now sitting as an Independent.

Sir Oliver explained this would allow MPs to move amendments to the government's proposal and for them to be voted upon if selected by the speaker, as mentioned above.

The SNP has tabled an amendment to reject the deal demanding an immediate extension to the October 31 deadline and a general election.

And Sir Oliver has put forward an amendment that, if accepted and approved, would withhold approval of the deal unless and until implementing legislation has passed.

There is a lot of talk about the Letwin amendment. What does Sir Oliver want?

Sir Oliver said the one issue that concerns him is keeping the Benn Act extension in place as an insurance policy until the implementing legislation is passed by both Houses of Parliament and the UK's withdrawal is ratified.

He said the purpose of his amendment is to "remove from the government's motion the bits that would have had the legal effect of satisfying the Benn Act conditions and would therefore have removed the need for the PM to seek an extension".

By way of explaining what has confused many, he added: "In short, my aim is to ensure that Boris's deal succeeds, but that we have an insurance policy which prevents the UK from crashing out on 31 October by mistake if something goes wrong during the passage of the implementing legislation."

What will happen if the deal passes?

If the prime minister is successful in Westminster, he will then have to hope that MEPs in the European Parliament give it the same backing - a point reiterated by European Commission president Jean-Claude Juncker in a joint press conference with Mr Johnson on Thursday.

Attention will also turn to passing the necessary legislation to make Britain's EU withdrawal legally enforceable.

The prime minister would need to find a further majority for the European Union (Withdrawal Agreement) Bill in order to put Brexit on the statute books.

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But what if the deal is rejected?

If Parliament does not support the deal, Mr Johnson is compelled under the Benn Act to request a further Brexit delay to the end of January.

EU Commission president Jean-Claude Juncker piled the pressure on MPs to back the deal by raising doubts over any further delay to the UK's departure past October 31.

But European Council president Donald Tusk said if there is a request for an extension he will "consult with other member states to see how they react".

How rare is a Saturday sitting?

The Commons has only sat on four Saturdays since 1939, including on September 2 that year, due to the outbreak of World War Two.

The last time there was a Saturday sitting was April 3, 1982, following the invasion of the Falkland Islands.

MPs also sat on Saturday, July 30, 1949, in order to finish up business before the summer adjournment as well as on Saturday, November 3, 1956, due to the Suez crisis.