REDRUTH, ENGLAND (NYTIMES) - Her cupboards are jammed with pasta, rice and couscous - enough to feed a family of five for weeks. Medications are crammed into plastic tubs, and in the garden of her four-bedroom home stands a 290-gallon water tank.

Mrs Nevine Mann is not readying herself for the threat of nuclear war, flooding or civil disorder in this part of Cornwall, in scenic south-west England. No, the spectre that keeps her on edge is Brexit.

Mrs Mann, 36, has joined the country's band of "Brexit preppers", people who fear chaos in March, when Britain will leave the European Union, and who are stockpiling supplies.

For more than 18 months, Britain has been trying to negotiate a deal with the European Union, without which the country could face gridlock at ports, trucks stuck on highways with their loads of food spoiling, empty grocery and pharmacy shelves, energy scarcity and factories shutting down.

Britain imports around one-third of its food from the EU, and businesses rely on complex supply chains that could break down if checks are imposed on the thousands of trucks that cross the English Channel each day.

This being Britain, people are not retreating to underground bunkers, as America's "doomsday preppers" do, and Britons are more likely to hoard toilet paper than weaponry.

But with time running out and negotiations at a delicate point, some Britons are preparing for a crisis that could upend their way of life.

"People are talking about World War II and rationing," said Mrs Mann, a former midwife. "People have also been talking about the blackouts in the 1970s, and how power was rationed."

"This has the potential of being a combination of the two," she said.

The government of Prime Minister Theresa May dismisses such talk, but its own ministers have published contingency plans for an exit on March 29 without a deal, and for the first time since the end of rationing in the 1950s, Britain has a minister responsible for food supplies.

More ominously, the government has advertised job openings in emergency planning.

Such measures may be intended to increase Britain's leverage in negotiations with Brussels, but they also signal to many people that there is a real possibility of a crisis, at least for a while.

A Facebook group called 48 Percent Preppers - named after the 48 per cent who voted in a 2016 referendum to remain in the EU - is dedicated to preparing for the impact of Brexit, and has more than 1,200 members.

Among the other advice circulating is a leaflet, "Getting Ready Together", that describes risks including reduced gas and oil supplies, shortages of food and drugs, and panic-buying leading to rationing.

"We can't change a lot of things, but we can be ready for the worst possible outcome, because nobody died from being over-prepared," said the leaflet's author, Mr James Patrick, a security consultant and former police officer. "We have a long history of being taken by surprise by predictable events."

Mr Patrick, who lives in the East Midlands region of England, says that people need not stock large quantities of food, and that his family has enough for only a week.

"This is a case of having some candles as well as a torch, a battery-powered radio, perhaps a solar-powered phone charger," he said, rejecting any parallel to doomsday preppers who prepare to barricade themselves in remote places with enough supplies for months or years.

"You just need two cupboards of food and some extra toilet roll," he said, "and coffee - because a lot of it comes through Germany - unless you fancy roasting acorns".

Mr Patrick has a podcast, "The Fall," that paints a more dystopian picture, however, anticipating that civil unrest could start on the first day of a disorderly Brexit "and increases exponentially after that" - a prediction that he denies is alarmist.

He noted that in 2011, an outbreak of arson and looting that "began literally over nothing" in London led to "a national incident that lasted for five days".

So divisive is the issue of Brexit that some of its supporters see "preppers" as alarmists who want to scare the population into rethinking the whole idea.

When Mr Howard Hardiman, an artist who lives on a remote Scottish island, wrote on Twitter that he was stockpiling because he lives at the end of the supply chain, he drew abuse online from supporters of Britain's departure from the bloc.

The government has repeatedly stated that there is no need for alarm, and that it expects to strike a deal soon with the EU.

An agreement would probably invoke a "standstill" transition period, during which few Britons would notice any changes until December 2020.

The EU says it, too, wants a deal, and it has made positive noises lately, though talks over the weekend failed to produce a breakthrough.

But even if the two sides reach an accord, it would still need approval from Parliament, where hard-line Brexit supporters in Mrs May's fractious Conservative Party are threatening to wreck any agreement because of her proposal to keep some close economic ties to the bloc.

Instead, they want a much cleaner break, with some insisting that there is nothing to fear from a no-deal Brexit.

Analysts say that the possibility of disorderly rupture cannot be discounted - something that brings with it the risk of disruption to supplies and a decline in the value of the British currency, which would in turn drive up the costs of imported food and other goods (another reason to stockpile).

Mr Ian Wright, the director general of the Food and Drink Federation, an industry group, said there was no sign so far of strains on supplies but predicted that stockpiling by consumers would start in earnest if there was no agreement on Brexit by next month.

The supermarket chain Tesco has said it is discussing contingency plans to keep more dried goods.

For those reliant on imported medication, a disorderly Brexit is a particular worry, and the government has asked pharmaceutical companies to store six weeks' supply of medication, though what would happen after that remains unclear.

Supplies might be flown in, bypassing clogged ports, but experts say a no-deal exit could also interfere with air travel, grounding many flights from the EU.

"I feel physically sick if I think about it," said Ms Jo Elgarf, a member of the 48 Percent Preppers group who lives in London and whose four-year-old daughter relies on imported drugs to stop seizures. Because they have to be prescribed, she cannot stock more than a four-week supply.

"There is no way I can protect my child, I am completely reliant on other people," she said.

Mrs Mann, who takes anti-epilepsy and blood-thinning drugs, also worries about medication, and she says she can do little other than make sure her prescriptions are up-to-date.

As for food, she says that she thinks she would be able to get local produce if shipping were disrupted, but admitted that she had became concerned at the end of last year, when Brexit negotiations were stalling.

So she started buying extra cans and more dried food and fruit - items with a long shelf life - when she went shopping every two weeks. Then, she added pet food (both her cat and her dog require special diets), and bought seeds to grow fruit and vegetables in the garden.

She has equipment to purify rain water, and her roof is covered with solar panels - though she is waiting for hardware to allow the panels to supply the house in a blackout.

Some of the darker predictions of food shortages causing disorder do not really weigh on Mrs Mann, who thinks it unlikely that Cornwall, less densely populated than the major cities, would see looting.

"We don't necessarily have to think about leaving and hiding in the woods or something because we are tucked away in the bottom end of the country," she said.

Mrs Mann acknowledges that the idea of stockpiling seems "surreal", but takes accusations of scaremongering in her stride.

"We are still going to use everything we've got," she said, "and, if we don't, then people are going to benefit from it through food banks."

"If we are panicking for nothing," she added, "does it matter?"