A ferry sails off the coast of Calais, the closest point in France to Britain. (Edouard Elias for The Washington Post)

“The Guv’nor!” is a red wine “stuffed with bramble and plummy flavours” that sells for about $5 a bottle, $30 a case. It’s a house specialty here at Majestic Wine Calais, one of the sprawling discount wine warehouses within walking distance of the English Channel. And it’s part of a cottage industry aimed at the steady flow of Brits who come by ferry to load up their cars with plonk far cheaper than at home.

But this journey, this industry, could be among the many casualties of Brexit — especially if Britain crashes out of the European Union without a withdrawal deal, as it’s set to do on April 12.

Peter Williamson, a 74-year-old retiree from Biggin Hill, outside London, is in the Guv’nor’s target demographic, though it was a Chilean white he was looking for at the Majestic warehouse last week. He said he was skeptical that wine would be much more expensive or less accessible after Brexit. “I think the French need the money,” said Williamson, who voted to leave the E.U. “They can’t turn away money from the British.”

But trade experts say that, absolutely, the landscape would shift.

“Today, wines are sold extremely easily. That will change completely,” said David Caron, a customs representative for CFDT, one of France’s largest labor unions. “They can return to the U.K. with a small quantity. But a whole trunk? Tomorrow there will be limits.”

Despite the hand-wringing that followed Britain’s 2016 referendum, the French seem largely resigned to the pending reality of Brexit. No European leader has taken a harder line against British political waffling than French President Emmanuel Macron. And, since January, the French government has had a detailed contingency plan for the increasingly likely scenario of a no-deal Brexit.

This is especially true in Calais, the closest point in France to Britain and a major transport hub. The port of Calais sees as many as 50 ferry departures and arrivals between the two countries each day, with a passenger flow of 10 million a year. Calais is also an entry and exit point for trucks — and 22 million tons of goods — traveling by rail through the Eurotunnel.

Many Brits make regular pilgrimages to Calais to buy wine, and perhaps have a nice French meal afterward. (Edouard Elias for The Washington Post)

The port of Calais built a new customs processing center to handle border inspections after Brexit. (Edouard Elias for The Washington Post)

How much this flow is disrupted by Brexit will depend in part on how Britain leaves.

If it departs with a withdrawal agreement, it will get a two-year transition period to sort out a trade relationship with the E.U. But if Britain leaves abruptly without a deal, it will lose its trade privileges overnight, and it probably will have to accept new tariffs, border inspections and document checks that weren’t necessary while it was a member of the unified bloc.

To prepare for that possibility, the European Commission last week adopted an emergency proposal to keep the Channel Tunnel operating normally for 90 days — provided Britain maintains “safety standards identical to E.U. requirements.”

The French government also has begun recruiting 700 additional customs officials. French unions say even more are needed, and to make the point, they have been staging strikes that have crippled Eurostar train services and created traffic jams near Calais.

But Jean-Marc Puissesseau, the Calais port boss, said he is confident his operation is ready. Last month the port completed a 6 million-euro customs processing center.

“This is a well-oiled machine,” Puissesseau said, as he noted on a color-coded map the new zones where Britain-bound trucks would be directed once they entered the facility.

Britain, too, has been rolling out contingency plans: reserving space on ferries, encouraging pharmaceutical companies to increase their supplies.

To be sure, having a sufficient supply of wine to last through Brexit is a lesser concern. But Jack Merrylees, a spokesman for Majestic, said some stockpiling was happening in Calais.

“The numbers certainly suggest that customers are taking the opportunity to stock up,” Merrylees said. “It’s clear that there is uncertainty and that it’s well worth getting the savings in now.”

Across the street from Majestic is the Calais Wine Superstore, another warehouse with aisles that seem to go on and on. Soft Frank Sinatra tunes play as customers scan new- and old-world reds and whites, and a selection of rosé that ranges from sunset pink to the color of nail polish remover.

Two British couples, sharing a car and travel expenses, stock up on wine in Calais. (Edouard Elias for The Washington Post)

In an appeal to British customers, prices are posted in pounds and euros at a discount wine warehouse. (Edouard Elias for The Washington Post)

Teresa Borcherds, 58, a retiree from Berkshire who in 2016 voted to remain in the E.U., said she and her husband usually come to the warehouse every three months and weren’t due back for at least another month and a half. But they came last week because of the pending Brexit deadline, she said.

What were they stockpiling? “J.P. Chenet — that’s wine,” she said. “And then lager and beer.”

This may be their last trip. “Thirty pounds for petrol on the way here, 30 for the fare, 30 for petrol again,” Borcherds said. “If you’re only buying cigarettes, it’s not worth it.”

Nearby were Ian and Joy Massif, 72 and 71, respectively, who were perusing everything but the French wines on offer. “We’ve got nothing against the French,” Ian said, laughing. “They operate a very good supermarket.” He added that their usual itinerary included a stop here, a stop at the nearby Carrefour grocery and then home. “No eating. No drinking. Home,” he said.

Both husband and wife voted to leave the E.U., and both were still concerned about the migrant situation in Calais, which, after the peak of Europe’s migrant influx, became a de facto holding pen for asylum seekers desperate to enter Britain, which mostly denied them entry.

“The last time we came we saw some just along the road,” Joy Massif said. “You locked your doors because you worried about it. And, of course, we’ve got them at home, with Dover being so close.”

Ian Massif pointed out that the two cases of wine on their trolley reminded him of the limits that used to exist before Britain joined the continental trade bloc in 1973. “Forty years ago, that would be your allowance — that’s it,” he said, noting that they planned to take home a load.

“We don’t drink it all ourselves,” Joy joked.

“We don’t drink it all at one time, either,” Ian said with a laugh. “There are so few pleasures left, aren’t there, darling?”

A gate at the port of Calais, where thousands of trucks going to and from Britain pass each day. (Edouard Elias for The Washington Post)