Everything you need to know about the Brexit Bill in five minutes

LONDON - MPs will on Tuesday and Wednesday debate whether the UK should trigger Article 50 - the two-year process by which Britain leaves the European Union.

The debate is expected to be long, confusing, and ultimately exhausting, so here's our brief guide to everything you need to know about the Brexit Bill, with help from the excellent Commons library.

Why are MPs debating Brexit? Didn't we settle this in the EU referendum?

Not really. The EU referendum bill passed by David Cameron did not contain any clause automatically triggering Brexit in the event of a Leave vote. This may not have mattered had the prime minister had the constitutional power to trigger it herself without first consulting Parliament. However, the Supreme Court ruled earlier this month that she doesn't. While the prime minister does have 'royal prerogative' powers on international relations, the court ruled that because Brexit will impact on UK domestic law, parliament must be consulted on it. As a result of this ruling Theresa May's government have published the European Union (Notification of Withdrawal Bill) which MPs will now vote on this Wednesday.

So what does the Bill actually do?

The bill contains just one operative clause which, if passed, authorises the prime minister to trigger Article 50. The bill has been deliberately tightly written to limit the ability of MPs to amend the bill. Under parliamentary rules any amendments to bills must be "relevant to the subject matter of the bill and to the clause or Schedule to which they are proposed."

So is that it? Will the bill just sail through Parliament?

Not quite. MPs have submitted dozens of amendments to the bill seeking to guide May's negotiating aims on everything from the single market to workers' rights and environmental protections. Other amendments include calls for the devolved administrations to be consulted and for the Brexit Secretary to report regularly to Parliament on the progress of negotiations. The chairman of Parliament's Ways and Means committee, Lindsay Hoyle will now decide which of these amendments are in order.

Can MPs block it altogether?

In theory yes. Dozens of MPs, including 19 Labour MPs have tabled 'reasoned amendments' to the bill. These are essentially wrecking amendments, which if passed, would block the bill from progressing through parliament. It is down to the Speaker of the House, John Bercow, to decide whether these amendments are in order. However, even if he does decide in their favour, they are highly unlikely to get enough support to pass.

So it's all over then. The Bill will pass?

Almost certainly yes. The decision by Jeremy Corbyn to impose a three-line whip ordering his MPs to back the Bill means that it should pass with an overwhelming majority. However, even without this whip there is a clear majority in the House for Brexit. A non-binding Parliamentary motion on triggering Article 50 was last year passed by a majority of 461 to 89 votes.

How about the Scottish government? Can't they block it?

First minister Nicola Sturgeon had argued that the Sewel Convention means that the devolved administrations must be consulted before triggering Article 50, because of the impact it would have on Scotland. However, the Supreme Court ruled this month that "on the devolution issues, the court unanimously concludes that... the Sewel Convention does not give rise to a legally enforceable obligation." The court ruled that the convention is just that - a convention. While the UK government may have a moral or political obligation to consult the developed administrations, there is no legal obligation on them to do so.

So it's checkmate then - we're definitely leaving the EU?

Not necessarily. This Bill is just the start of the process that will take us out of the EU and there are still several other hurdles to jump before we do so. Once the Bill is passed MPs will then have to vote on the Great Repeal Bill which will start the process of revoking EU laws. There is also an upcoming legal case which could force the government to consult MPs on Britain's exit from the European Economic Area and the single market. If this case is successful May could have greater trouble getting it through parliament.

Can we change our minds?

We don't know. UK courts have so far not ruled on whether Article 50 is revocable but there is a considerable body of legal opinion that it is. Under international law there is precedent for withdrawing states to be allowed a "cooling off period" in which they can change their decision. Lord Kerr, who drafted Article 50 itself, has also said it is reversible while Donald Tusk, President of the European Council, has stated that Britain could decide to stay in at the end of the two year Article 50 period.

There is also a case currently pending in the Irish High Court which, if successful, could lead to a referral to the EU court of justice on the question of whether Article 50 is reversible. While the UK government have stated that they have no intention of seeking to reverse Article 50 there is still a possibility that they may seek to extend the two-year exit period. This is not as straightforward as it sounds however. Under the terms of Article 50, any extension would require the consent of all other EU nations, some of which may wish to get us out as soon as possible.

So when does this all start?

MPs will begin debating the bill on Tuesday before voting on its second reading on Wednesday. It will then go to a committee of the whole house, probably on February 6 before the remaining stages of the bill are debated on February 8. If any amendments to the bill are passed it will then go for a Reports stage before passing to the House of Lords, most likely after the February recess which ends on February 17. The government then hopes to have the whole thing wrapped up by March 7, weeks ahead of its deadline for triggering Article 50, which is March 31.