London(CNN) Tick, tick, tick.
The countdown to Brexit can now be measured in weeks, if not quite days -- and with time running out for an alternative way forward, Britain and the European Union are currently hurtling towards a no-deal split.
It's the outcome that Theresa May, the country's opposition parties, and a majority of lawmakers in Parliament have been working for three years to avoid, and it's shrouded in warnings from economists and business leaders. But after politicians repeatedly failed to agree on another path, a no-deal remains the default option -- unless MPs are unable to pass legislation to block it.
Confused? You're not the only one. Britain's Brexit paralysis has long resembled a tangled web of claims, counterclaims and outright shouting matches.
But we can help -- here's what you need to know about no-deal.
If Britain reaches the October 31 Brexit deadline without having a withdrawal agreement in place, the legal default is that it will just leave the EU without one.
In an instant, the country would lose its access to the EU's single market and customs union, which facilitate trade between the bloc's members. All manner of legal arrangements agreed by EU bodies will no longer apply in the UK, and businesses, public bodies and citizens would have to respond to the changes that leaving the EU would bring.
Some Conservative MPs have been arguing in favor of a no-deal Brexit, on the basis that it would immediately increase Britain's freedom to manage its own trade deals, laws and border arrangements.
Britain would revert to World Trade Organization (WTO) rules, and would be free to negotiate trade pacts with other countries, such as the US, as well as with the EU.
It would also be able to set its own immigration laws, as it won't be bound by EU freedom of movement commitments.
And for many of the 17 million people who voted for Brexit, no-deal is appealing simply because it means Brexit will happen -- after a lengthy period of uncertainty in which the deadline has been delayed twice, and swirling speculation over the possibility of a second referendum which could cancel out the first one.
The main certainty is uncertainty. Britain would be in uncharted waters if its splits from the EU overnight, and that would probably have an immediate impact on the strength of its currency.
The UK would likely face food, fuel and medicine shortages, according to the forecasts compiled by the Cabinet Office under the code name "Operation Yellowhammer," which were leaked last month.
That dossier also predicted the introduction of a hard border in Ireland, which has been a main sticking point in negotiations, and severe travel disruptions at UK ports that could last up to three months.
Medical supplies coming from Europe will be "vulnerable to severe extended delays," and the availability of fresh food will be reduced, causing prices to rise, the leak revealed.
But Michael Gove, the British minister responsible for planning for a no-deal Brexit, said after the leak that operation Yellowhammer was a "worst-case scenario" and that "significant steps have been taken in the last three weeks" to accelerate planning. Some have also disputed the accuracy of the report. The Government of Gibraltar -- which is a British territory on Spain's southern coast -- also told CNN the briefings were "out of date" and based on planning for worst-case scenarios which it has "already dealt with."
As for travel, people seeking to head in or out of the UK face so many uncertainties in the event of a no-deal that it's almost impossible to plan effectively to avoid them.
Downing Street has confirmed that freedom of movement rules for EU citizens will change "immediately," with tougher criminality checks among the amendments. Further details on the changes are to be set out in due course.
There are a number of routes which those opposed to a no-deal could still pursue, but time is running out.
The first path is legislative: MPs voted on Tuesday to take control of the parliamentary order paper from Boris Johnson's government, allowing them to debate a bill that would rule out a no-deal Brexit and force the government to ask for another Brexit delay on Wednesday.
Johnson reacted to the rebel move by announced he will seek an early election if MPs force his hand. The opposition has ruled out backing another election until no-deal is ruled out, but one can't be far way.
An election could certainly change the course of the Brexit process, if it swings Parliament further behind or against a no-deal. Johnson could return with a healthy majority in favor of an immediate split from the EU -- or he could be forced out and see a no-deal wiped off the table.
And, for the optimists -- Johnson could still secure a deal with the EU in the coming weeks, which if passed by Parliament would avert the need for a no-deal Brexit.
But a no-deal Brexit remains the legal default, and it's impossible to avoid on October 31 unless a new law is passed -- in agreement with the EU -- that says otherwise.
So any attempt to stop it has at least two formidable opponents -- the government, and the clock.