A pro-EU demonstrator holds up a placard outside the Houses of Parliament | Adrian Dennis/AFP via Getty Images 5 levers to tackle the economic shock of no-deal Brexit None of the weapons at the UK’s disposal comes without downsides.

It's 11:01 p.m. in London on Friday, March 29 and it's no deal. Britain will need to take immediate action to try to shield the economy from shocks, probably before markets open, on April Fools' Day.

Here we take a look at some of the emergency levers that U.K. policymakers can pull.

Britain's import-dependent economy has never looked so vulnerable in peacetime. An inflation bomb is set to explode. A diving pound and tariffs on key products from the EU such as food would hit consumers hard. Britain runs a hefty trade-in-goods deficit (of about £130 billion in 2016 and 2017), and sources about half of its food from abroad.

Policymakers will have to make hard choices on how to manage the currency — particularly on whether to hike or cut interest rates — when core elements of the economic model will be under fire. Markets have traditionally been tolerant of U.K. debt and deficit levels because the country was a prime venue for foreign direct investment from big companies such as Airbus and Nissan, but these are now in question.

As Bank of England Governor Mark Carney put it, Britain relies on the "kindness of strangers." This has been drying up because the U.K. is becoming a less attractive investment destination outside the EU single market. Foreign direct investment more than halved to $15.1 billion in 2017, from $32.7 billion in 2015, according to U.N. figures.

Here's our look at the five responses that the U.K. will need to consider. All have disadvantages.

1. Drop import tariffs to avoid big price hikes

If Britain leaves the EU without a deal, tariffs would be imposed on imports that used to come in freely from the EU. For example, Britain's tariff on beef purchases would be around 40 percent.

To avoid food price inflation, Britain could lower or completely scrap tariffs on things such as food, car parts or medicines.

Catch No. 1: The World Trade Organization’s “most favored nation" principle dictates that these tariffs must be the same for all WTO members, unless you're in a trade deal or in a regional bloc like the EU. This means not only French but also South American beef or cheese would come to Britain tariff-free.

Farmers would lose out, as cheap imports undercut their products. The government's brutal calculation would have to be that farmers are far less important to the economy than supermarket prices for the whole population.

Trade Secretary Liam Fox told the U.K. parliament’s international trade committee on Wednesday that waiving tariffs to stimulate trade is a “possibility.” But the “full liberalization of tariffs … would certainly expose the U.K. to sudden competition in sectors to which it’s not currently,” Fox said.

Catch No. 2: By slashing tariffs, you have effectively gifted away your leverage in trade negotiations with other partners. They will already be shipping their goods tariff-free, they don't need a deal. British tariffs may be down, but those of trade partners won't be — putting British exporters in a difficult spot.

2. Use the Article 21 ‘nuclear option’

A hard-line solution would be to only lower tariffs to EU imports and ignore the WTO rules. Other countries would probably complain and launch WTO disputes, but Britain could fend them off by calling on Article 21 of the WTO rulebook, the infamous "national security" exemption, favorite of Donald Trump.

British Conservative MEP David Campbell Bannerman suggested this option in a Telegraph op-ed last month, saying the "national security" justification is possible because Britain would be "seeking to avoid security issues at the Northern Ireland border."

Article 21 has long been a taboo in the trade world, but over the past one and a half years it has gained some dubious popularity as the United States, Russia and the United Arab Emirates invoked the exemption to justify questionable actions such as protective tariffs and border restrictions. The EU is a sharp critic of such steps and has warned that abusive use of Article 21 risks undermining the entire multilateral trading system.

Triggering this "nuclear option" would be risky for Britain too: “It would be an incredibly damaging way for the U.K. to start its new role as an independent member of the World Trade Organization,” said Dmitry Grozoubinski, a former Australian WTO negotiator. He warned that using such an "excuse for breaching most-favored nation rules" could backfire as Britain would likely use all the goodwill it would need in other talks, both bilaterally as well as at the multilateral WTO level.

3. Rates. Should I cut or should I hike?

Money is Britain's supreme challenge. Many economists think the Bank of England will probably inject the markets with fresh money to try to prevent a meltdown. But this will also come at a cost for consumers, who will have to face higher prices.

Those looking to give the economy a shot in arm also reckon that the Bank of England would likely slash the base rate from the current 0.75 percent, accepting that this will exacerbate inflation.

Such a cut is not guaranteed, however. The Bank of England's Carney has warned that businesses should not rule out an increase in the base rate. While this would help bolster the pound, a hike poses big challenges in the U.K., where mortgage debt is high and higher rates could create a housing crisis and sap household spending.

The political risk is that deregulation could mean lowering standards on things like food safety, scrapping checks on dangerous chemicals, environmental protection, unemployment, or health benefits and consumer rights

According to the Bank of England, Britain’s economic activity would fall by as much as 8 percent in the case of no-deal. The bank warned that in this scenario “output falls by more than it did in the financial crisis.”

One of the biggest immediate risks on Brexit day is that banks stop lending money to businesses or even to each other, out of fears that they won’t get their money back.

“Like at the moment when Lehman Brothers collapsed or 9/11, the central bank would certainly respond by injecting short-term liquidity,” said ING Chief Economist Carsten Brzeski.

In order to stimulate growth, the BoE may then want to use quantitative easing. “You will have to ask yourself how much you can stimulate without driving up inflation,” Brzeski said. “The pound will be weaker, so there will already be what we call imported inflation.” Further monetary loosening would make this worse.

Another of Britain's vulnerabilities is that economists caution that a weak pound is not unadulterated good news for exporters. Many manufacturers insist they would prefer a stable to a weak currency because they are so dependent on imported raw materials and components.

4. Stop customs checks

Slashing tariffs will help soften the blow of higher food prices on consumers. But it won't help businesses whose shipments are stuck in ports. Customs checks could lead to kilometers of trucks at highways and at the entrance to the Channel tunnel.

That will be one of the main costs of a hard Brexit, some economists say, in that it disrupts supply chains and ruins businesses that rely on just-in-time production. That's why some businesses and pharmacies have started stockpiling supplies.

To avoid such a mayhem, the U.K. government could decide to wave through imports at its ports. It has already announced that it would do so for EU goods.

The risk of that is obvious: Suspend customs checks for too long, and Britain could become a smugglers' paradise.

The EU may not do the same for U.K. exports coming in, meaning British exporters will struggle to get their merchandise into their biggest market.

The longer this situation persists, the more manufacturers would move their factories into the EU, meaning the U.K.'s trade deficit could widen.

5. Deregulate to become a fiscal paradise

This is the dream of hard-line Brexiteers like Jacob Rees-Mogg and Daniel Hannan. Once Britain leaves the EU without a deal, it could become a fiscal paradise, dropping taxes and deregulating its industry. This could attract investors as France and Germany show signs of pursuing a more protectionist model.

This is a longer-term solution, however, and will do little to resolve instant shocks.

The political risk is that deregulation could mean lowering standards on things like food safety, scrapping checks on dangerous chemicals, environmental protection, unemployment, or health benefits and consumer rights.

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