The 27 EU heads of state and government will allow a flexible extension to Brexit until January 31, European Council President Donald Tusk revealed on Monday. 

The so-called "flextension" will mean that the UK can leave before that date if they manage to agree a deal in Parliament.

UK Prime Minister Boris Johnson sent the request for a delay, albeit reluctantly and unsigned, last weekend as the result of legislation that effectively forced his hand.

Read more:  Key vote on Brexit deal debate fails in Parliament

Now that an extension has been granted, what happens next in Westminster? How might British politicians try to break the 41 months of deadlock since 2016's referendum? Three scenarios seem most likely:

Option 1: Extension, no election, try to finalize deal

The quickest way out is for Boris Johnson's minority government to try to push its existing Brexit deal through Parliament. However, that will require at least some opposition support because the Conservatives fall well short of passing a deal by themselves. 

The deal risks either not passing Parliament, or being altered in ways the EU might object to, which could also scupper it.

The benefit to choosing this route, from the point of view of many MPs, would be completing the first stage of the Brexit process before returning to the voters in a general election. Almost all sitting Conservative and Labour MPs pledged during 2017's campaign to take the UK out of the EU, in one way or another, in order to fulfill the referendum decision. 

Johnson has told the opposition that if they agree to his desired December 12 date for new elections, he would grant further time to debate and sign off on the deal before dissolving Parliament for the campaign. Should they refuse this, Johnson has effectively threatened to put the government on strike and halt all but the most necessary business. 

Option 2: Extension, election, Conservatives win 

Whether it comes before or after Parliament passes plans to leave the EU, the UK seems doomed to a general election sooner than later.

The prime minister will need opposition support to trigger an early election, but Labour's leadership has indicated likely willingness for such a vote once an extension is secure.

Current polls suggest that the Conservatives would win a majority if a vote were held now. That said, polling rates have been immensely volatile ever since 2016's referendum. In 2017, Theresa May called an early election expecting a huge majority, only to see her support tank and Labour's soar during the campaign. 

Should the Conservatives win a majority, though, their route towards passing Boris Johnson's deal would appear to be clear.

Option 3: Extension, election, change of government

If Labour wins a majority outright, or various opposition parties unite to form an anti-Tory coalition, then the way forward becomes more murky. What seems certain, though, is that the winners would ultimately need a far longer extension than just three months. 

Any non-Conservative government — even a coalition — would almost certainly be led by Jeremy Corbyn's Labour Party, so it is a reasonable assumption that their proposed Brexit plan would be used as a blueprint. 

Corbyn's party, if elected, is pledging to renegotiate a different, softer deal with the EU, and then to put that deal to the people in a referendum, against the option to remain in the EU.

Each stage of this process would surely take several months — assuming Europe's patience endured. But the added delay would be sweetened by the potential prospect of the EU retaining all 28 of its members.

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