THE lure has always been powerful. Why negotiate with an organisation you dislike, which also wants to erode any gains from leaving? Why not just walk out? After all, no deal is better than a bad deal, as Theresa May has often said.

Talk of a no-deal Brexit has revived strongly since the prime minister laid out fresh negotiating objectives in a meeting at Chequers, her country house, last month. Tory MPs report deep dissatisfaction in the party with the plan, which many Brexiteers think gives too much to the EU. Two cabinet ministers resigned for the same reason. Worse, Brussels wants more. Mujtaba Rahman of the Eurasia Group, a consultancy, says that behind the EU’s cautious public welcome for Chequers, the private view is very negative.

Faced with such recalcitrance on all sides, Mrs May is reviving no-deal planning. Dominic Raab, her new Brexit secretary, talks of stockpiling food and medicine. Jeremy Hunt, the foreign secretary, says the probability of no deal is increasing by the day. The government will soon publish advice to businesses and individuals of the possible impact. The European Commission has issued similar notes.

A no-deal Brexit sounds simple, but it comes in several guises. One is as a negotiating tactic, to strengthen Britain’s weak bargaining position. But this works only if the threat of no deal is credible, and few people in Brussels think it is. Another of its purposes is to win more support at home for Mrs May’s Chequers plan, by showing voters the horrors that would result from rejecting it. So far, this is not working, either. Polls find that voters prefer no deal to Chequers by two to one.

That may be because they think a no-deal separation would be amicable. Both sides could agree to minimise disruption to flights, food supplies and so on. Yet a friendly no deal is implausible. Whether it happened by accident or design, it would now mean Britain rejecting previously agreed terms, notably a £40bn ($52bn) exit bill, a guarantee of EU citizens’ rights and averting a hard border in Ireland. That would surely make a no-deal exit acrimonious, thereby aggravating its effects. A new study by the IMF finds that these would be bad for all EU countries, especially Ireland and those near the Channel. But they would be worst for Britain (see chart).

Many Brexiteers refuse to accept this. To see why they are wrong, start with trade. Brexiteers argue for trading on World Trade Organisation (WTO) rules, as most non-EU countries already do. Yet with no deal, Britain would be the only big country trading solely on WTO terms. Others, even those without trade agreements in place, have side deals to facilitate customs inspections. Reverting to the WTO is also tricky. Britain is a member, but to take up its rights it must divide import quotas with the EU. Efforts to do this have been opposed by America, Brazil and even New Zealand. Nor would trade with other countries be trouble-free. Britain benefits from the EU’s trade deals with 50-odd countries, including Mexico, South Korea and Japan. Britain hopes to roll these over after Brexit. But that requires the EU’s assent, which would be unlikely after a no-deal outcome. The other countries must also agree. David Henig, a former trade negotiator, says they would impose harsh terms, given Britain’s weak position. Customs would be a big problem. Brexiteers say Britain should keep its borders open, without controls or tariffs. Yet the EU would be unable to reciprocate, not least because WTO rules say that tariff-free access would have to be offered to all members. The number of customs forms for exporters would quadruple, costing £20bn a year. An extra two minutes’ delay for lorries at Dover would mean long queues in Kent. Unilateral free trade would ravage British farming and manufacturing. And one-way free trade does not help lorry drivers, who must return fully laden. No deal also means a hard Irish border. Again, Brexiteers say London and Dublin could agree not to have one. But with no deal, that would be illegal under the EU’s own rules, as well as those of the WTO. Agrifoods, which account for most of the trade across the border, would be badly affected. As well as tariffs, EU food-safety checks would have to be applied, to avoid Northern Ireland becoming an open conduit to evade them. A hard border would rattle the delicate peace process.

Then there are British firms’ supply chains. These are now widely spread across the single market. Supermarkets and carmakers alike rely on just-in-time deliveries that would be disrupted by a no-deal Brexit. Switching to non-EU sources would take time and money. So would stockpiling supplies, which for most businesses is impractical (see article).

Regulatory obstacles would be even worse. A no-deal Brexit would take Britain out of all the EU’s agencies, as well as its courts. Brexiteers may welcome this, but setting up alternatives would take years. The EU is clear that trade in goods like chemicals, pharmaceuticals or cars depends on Britain meeting its standards. Britain’s car industry, which employs 800,000 people and exports 80% of its output, is especially vulnerable, as it would lose EU certification for vehicles, as well as facing 10% tariffs.

There are no domestic regulators to replace the European Medicines Agency and the European Aviation Safety Agency (EASA). The first would stop drug exports, but also imports like insulin that may require re-testing. Radio-isotopes needed for cancer treatments could not be imported after Britain leaves Euratom. Outside EASA, airlines could not fly within Europe. Rules requiring majority EU ownership could cause problems for airlines such as British Airways.

The list goes on. A priority for Brexiteers is to stop free movement of EU citizens. But shortages of border guards and the lack of any registration system will make this impossible for many months. So free movement would be likely to continue even after a no-deal Brexit, says Joe Owen of the Institute for Government, a think-tank. Security co-operation would also suffer as Britain fell out of the European Arrest Warrant and intelligence databases.

Brexiteers may call this Project Fear 2.0, but the evidence is against them. Market confidence would suffer. John Springford of the Centre for European Reform, a think-tank, says a no-deal Brexit would trigger both a recession and a run on the pound. No deal is not a serious option, even if today’s febrile politics pretends it is.