Martin’s dressed-down, folksy image and hands-on reputation have earned him many supporters. He visits several of his pubs each week to check on everything from bar service to bathroom cleanliness.
But has Martin's stance on Britain’s most divisive issue in memory left a bad taste in the mouth of some customers?
“As far as I’m aware nobody has thrown down their pint and walked out into another pub,” he told NBC News over a drink at his barn-like Shakespeare’s Head pub in London’s Holborn neighborhood. “I think people on the whole have accepted that it’s fair enough to have a debate."
Two years after the shock referendum result, the U.K. remains intractably divided on what Brexit should look like, or whether it should still go ahead at all.
Martin, 63, wants Britain to push ahead and completely quit the European Union customs zone — a so-called “hard Brexit” that he believes would reduce the price of food for his drinkers.
Many other British business leaders are opposed to that idea, but Martin says they are trying to fool the public.
“We should be friends with Europe but get the hell out," he said.
Among customers in the Shakespeare’s Head, not everyone knows who Martin is or cares what he thinks, but Brexit remains a raw topic.
“I just want to drink in peace," said Dennis Meleady, 63. "I hear enough rubbish about politics in the news without getting it in here.”
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The retired carpenter voted for Brexit, but now has doubts that it will ever happen. “It’s a complete mess,” he said.
Britain has already triggered the E.U.'s divorce mechanism and will leave the bloc in just 243 days’ time on March 29, 2019.
However, political maneuvering over post-Brexit border arrangements has mired Prime Minister Theresa May's ruling Conservative government in a series of crises. It narrowly avoided a defeat in the House of Commons on one vote earlier this month, scraping by 305 to 302 to earn a narrow victory against the opposition.
Growing uncertainty at the impact on trade and customs has prompted some lawmakers from across the political spectrum to demand the process be subjected to a second vote or even abandoned altogether.
Martin said the passion on both sides of Brexit debate was reminiscent of the 1970s sectarian “Troubles” in Northern Ireland, where he grew up.
"It’s amazing how people’s emotions have been engaged," he said.
That's at least partially because many E.U. citizens living in Britain face an uncertain future, with their immigration status still unclear.
“My parents are immigrants,” said Daniel Varao, a security manager drinking a cold pint of cider. “My parents are from Portugal, they’ve been here for more than 40 years. They’ve paid their taxes, I was born here, my sister was born here. As every day comes closer to Brexit, the reality is kicking in. Will they be threatened with being kicked out of the country they’ve been in for 40 years?”
Florian Radoi, a 31-year-old construction worker from Romania smoking a cigarette in the sunshine by the pub entrance, said: “Who is going to do these jobs, if we are not here? We are thousands in London.”
Beer expert Pete Brown believes Martin has “violated the sanctity of the boozer” by “politicizing” his watering holes.
"Some people do talk politics in the pub among themselves, but this Brexit campaign feels a bit like the bartender leaning over out of the blue and telling you what they think," he said. "A great publican creates an environment where people feel relaxed and welcome. Having a strident view on an issue feels like that trust has been broken."
He added: "My local Wetherspoon is one of the few places left where you see a real cross-section of the community — people of color, older people, students, shift workers — it is inclusive like a pub should be. That's why it rankles with me to see a political campaign."
Martin thinks discussion is healthier than polite silence.
“I ardently believe in Brexit and in democracy,” he said. “One of the great things about democracy is that it brings out debate, it brings out tremendous emotion and emotion is energy.”
The chain has a reputation for cheap drinks and a music-free, no-nonsense environment that, like Brexit, drinkers either love or hate.
Martin founded his empire with a single pub in north London in 1979 and has steadily expanded as an outsider competing against Britain’s complacent, brewery-controlled pubs. (He named the business after “J.D. [Boss] Hogg” from the Dukes of Hazzard and one of this former school teachers, Mr. Wetherspoon.)