Brexit uncertainty is the only sure thing

Confusion reigns with less than four months to go until UK leaves the EU

In 1952, pollution and atmospheric conditions resulted in an incident known as the Great London Smog, which saw the city cloaked in a thick, unhealthy fog. The government's response was the Clean Air Act of 1956, to ensure it was never repeated.

Look at London in 2018, however-specifically the area around the Houses of Parliament-you could be forgiven for thinking the Clean Air Act never happened. Rarely has the outlook been less clear.

With less than four months left until Britain's scheduled exit from the European Union on March 29, confusion reigns. The Brexit process set in motion by the 2016 referendum called by then-prime minister David Cameron, which was won 52 percent to 48 percent by the Leave campaign, has caused political turbulence rarely seen in Britain in living memory outside wartime.

Before terms have even been agreed, Brexit has already cost Britain endless working and broadcasting hours, numerous falls in the value of the pound, a prime minister (Cameron left office once the result was announced), one foreign secretary (Boris Johnson resigned in protest at the government's handling of the issue in July 2018) and two Brexit ministers (David Davis and Dominic Raab, who also quit their posts)-and it could yet bring down Prime Minister Theresa May.

At the end of November, after a bruising internal debate which saw the resignations of Raab and another minister, May's proposals for terms for Britain's departure received Cabinet backing and, days later, the approval of the leaders of the other 27 EU member states.

Now she faces an even bigger challenge-securing Parliament's backing in a debate which begins on Tuesday. It will be fierce, with staunchly held opinions on all sides, and little mood for compromise. Its outcome-and the consequence-are anyone's guess.

At the moment, whether or not divorce terms have been agreed, Britain is leaving at the end of next March. If there is no deal, however, the complete lack of certainty affecting so many aspects of the daily functions of national life, such as imports of food and medical supplies, international travel and the employment and residency status of many foreigners living in Britain, could be huge.

Brexit supporters have dismissed talk of supermarkets and medical services stockpiling supplies as "Project Fear", but it is impossible to predict with any certainty what would happen, and few politicians would want responsibility for causing such upset.

If there is no deal, or Parliament rejects May's proposal, providing the other EU members agreed to it, March's departure deadline could be extended. May could be given a second attempt at securing parliamentary approval.