As far as understatements go, to say the next three months are going to be rather tense and unpredictable is up there with pilot Eric Moody's announcement to passengers on board British Airways 747 as it it flew into a volcanic ash cloud above Indonesia in 1982.

"Ladies and gentlemen, this is your captain speaking," he said, "we have a small problem. All four engines have stopped. I trust you are not in too much distress."

(Despite falling 25,000 feet, remarkably, Captain Moody was able to make a safe emergency landing in Jarkarta.)

How this Brexit story ends however, is anyone's guess. What we know for sure is this: the Brexit deadline is October 31st 2019.

The UK voted to leave the EU three years ago but the issue remains as divisive as ever, despite the deadline drawing ever nearer. Credit: AP

Boris Johnson has promised that Britain will leave the European Union on that date, deal or no-deal.

A majority of MPs in Parliament do not want to leave without a deal.

Right now, the chances of a deal between the UK and the EU are slim. Slimmer than slim and slimmer still.

The PM says the current Withdrawal Agreement is dead - it's been voted down three times by Parliament and unless the Irish backstop is removed, he won't even bother going to Brussels to meet with EU leaders because there is simply no point.

The European Union says the Withdrawal Agreement is the "best deal possible" - it won't remove the Irish backstop and is happy to speak "on the phone or in person" to reiterate this position.

So we're stuck. Deadlock. The default option therefore is no-deal.

Which brings us back to Parliament.

For years the Houses of Parliament has been home to anti and pro-Brexit demonstrations. Credit: AP

Can MPs actually stop Britain leaving without a deal?

Well their first port of call would probably be a no-confidence motion to try to bring down the government.

Labour leader Jeremy Corbyn has signalled he could to table such motion in early September when MPs return from their summer break.

With the government's majority in the Commons down to just one, it would only require a handful of Tory rebels opposed to no-deal to join the opposition to defeat the government.

But, that wouldn't necessarily stop Brexit or Boris Johnson.

Under the Fixed-Term Parliaments Act (FTPA), MPs have 14 days in which to pass a motion of confidence in either Mr Johnson’s government or an alternative government.

If it fails to do that, there has to be a general election.

Former attorney general and Tory backbencher Dominic Grieve has suggested MPs would try to form a cross-party "government of national unity" to seek a new extension of the Brexit date from Brussels while Parliament works out what to do next.

In that scenario, Mr Grieve says Boris Johnson would have no choice but to stand down as prime minister if MPs support a new government.

However, Dominic Cummings - Mr Johnson's special advisor and the man basically running Downing Street - is reportedly hatching a plan for the prime minister to ignore Parliament and instead move straight to calling a general election.

Dominic Cummings (L) and Dominic Grieve are on opposite sides of Brexit. Credit: PA

Crucially, it would be up to Mr Johnson to decide the election date, which he could delay until November, by which point Britain would be out of the EU and it would be too late for any new government to do anything about it.

Constitutional experts say that under a strict reading of the FTPA there is no requirement on the prime minister to resign, even if MPs were to support an alternative government.

That would cause almighty political row the likes of which Britain has not witnessed for centuries, potentially dragging the Queen into a constitutional crisis which would almost certainly end in the Supreme Court.

Right now, Downing Street are "not engaging in hypotheticals" but insist that whatever happens, Britain will be out of the European Union on November 1st.

Inside Number 10, Boris Johnson and his team are preparing for the battle of their lives to live up to that promise.