London (CNN) Boris Johnson, the UK's new Prime Minister, has inherited an unprecedented constitutional mess from his predecessor, Theresa May.

So, while the UK might have a new Prime Minister, it doesn't have a new Parliament. Before long, Johnson is going to have to face up to this reality.

At a glance, Johnson's Brexit plan is simpler than May's: get a new agreement with the EU or crash out on October 31 with no deal. Given that the EU has said numerous times that May's deal, formally known at the Withdrawal Agreement, is not open for renegotiation, no deal seems on the cards.

The snag for Johnson is that among those rejected Brexit alternatives was, you guessed it, no deal. On paper, that leaves the UK in what would be commonly called a constitutional crisis.

The UK is unlike most Western nations in that it has no written constitution. Instead, it relies on constitutional precedent and convention set out in law or previous acts of Parliament.

However, Brexit has thrown up so many political abnormalities that with no precedent or written constitution to fall back on, the political class has started trying to make it up as it goes along.

"The problem is that there are numerous things going on with the constitution, and a lot of it in new, completely untested areas," says Catherine Haddon, a senior fellow at the Institute for Government. "Even though certain things are written down in law about what happens when, how it actually happens is untested territory."

This constitutional ambiguity has led to an almighty row about what should happen next.

When Parliament returns from its summer holiday on September 3, Johnson could well face a motion of no confidence in his government.

It's a vote that Johnson and his team can't expect to win. He currently has a parliamentary majority of just one. And some of his own Conservative lawmakers have implied they will put blocking no deal ahead of party loyalty.

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However, losing this vote wouldn't mean that Johnson gets stopped in his tracks. Nor would it mean that no deal is automatically avoided.

After losing a confidence vote, the sitting government by law has 14 days to try to win back the confidence of the House of Commons and resume governing. If it fails to do so, then an early general election is called. Until the result of that election, a caretaker government (probably the sitting government) runs the country.

The problem with all of the above is that the law on which it relies, the Fixed Term Parliaments Act, only came into being in 2011, meaning there is no precedent in using it to kick out a government. "While it (the FTPA) tells us about a procedure whereby an early election can take place, it doesn't help with the nitty gritty, like when does the government have to go and how do you replace it," says Andrew Blick of the UK's Constitutional Society.

The law itself doesn't specify exactly when this election would have to take place. This means that, despite losing a confidence vote, Johnson would effectively be able to sit in Downing Street for weeks, if not months.

Even under normal circumstances, a caretaker government would be far from ideal in a nation used to governments with clear parliamentary majorities. But with the Brexit deadline looming, the UK faces an autumn crunch point.

The next EU Council Summit takes place on October 17 -- two weeks before Brexit day. It is, currently, the only chance the UK has to delay Brexit and avoid no deal. It would be up to whoever is leading the government at this point to represent the UK. If that person is Johnson, it would be solely in his gift to request an extension. Should he opt not to, then May's deal remains unratified in London and Brussels, meaning the clock runs out and it's all over.

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Not everyone agrees that this is the only outcome. Dominic Grieve, the UK's former attorney general, thinks that, given the unprecedented crisis, lawmakers should try to form a cross-party caretaker government of national unity during the 14 day-period after Johnson loses a confidence vote.

This caretaker government would be able to request a Brexit extension from the EU, possibly by letter, giving the UK time for an election and to get its house in order. Unfortunately for Grieve, this too is entirely without precedent and relies on constitutional norms being made up on the spot. All the while, it would be perfectly legal for Johnson to remain in power, running down the Brexit timer.

Even if Johnson does choose to sit tight, some lawmakers believe they can force his hand to delay Brexit. In recent days, those opposed to no deal have pointed to something called the Cabinet Manual, which advises a caretaker government on what it should and shouldn't do.

Once crucial observation it makes is that a caretaker government doesn't have the confidence of the House of Commons. Therefore, as Haddon points out, one way it could be interpreted is that a caretaker government would be "restricted in what they can do and ought to act in the national interest with the opposition parties."

However, even this is just guidance. And as the chairman of Johnson's Conservative Party said recently, any government headed up by Johnson is "not going to initiate a general election" before October 31. So, no deal's back on the cards.

Without a written constitution and no precedent for guidance, this all becomes a political battleground. In recent weeks, all sorts of wild suggestions have been made.

Some have even suggested that the Queen, the UK's conventionally apolitical head of state, could get involved.

However ludicrous this seems, Blick says that "the only firm legal position in all of this is that, in theory, the Queen appoints and can dismiss a prime minister."

And as Blick points out, "because there are such sharply diverging interpretations being advanced, it could become harder for the politicians to sort this out between themselves ... I'm sure the palace is concerned by this."

From squatting prime ministers to a writing letters to the EU and the Queen sacking Boris Johnson, Brexit can feel pretty surreal. However, with absolutely nothing to guide the UK's politicians through this mess, it's hard to see squabbling lawmakers ending this nightmare any time soon.

And just as three years ago leaving the EU without a deal seemed far-fetched, only a fool would rule anything out at this point.