Jacob Rees-Mogg, the man at the centre of Britain’s most unlikely political cult, has arrived early. The vintage Bentley is parked outside, and the owlish 48-year-old is sitting in a country pub in a double-breasted blue suit, his side parting unchanged from the days when his nanny patted his hair and sent him off to prep school. This is a pub lunch, Rees-Mogg style. He beckons me to a table by a picture window, offering sun-drenched views of his ancestral homeland: the rolling Somerset hills near Bristol in the south-west of England. “It’s an honour,” he says, by way of introduction, in his familiar establishment drawl.

These have been busy times for the fogeyish arch-conservative MP. This summer he celebrated the birth of his sixth child, imaginatively named Sixtus (Rees-Mogg says he has been ribbed that his next might be called “Septimus and Octopus”) — he also improbably emerged as a possible future prime minister. Rees-Mogg recently mischievously posted on his Instagram page a satirical article suggesting he was “sent from 1923 to save the Conservative party”. But over the summer something strange happened. Party activists started to entertain the possibility that the cartoonish toff sitting bolt upright opposite me in the Pony and Trap pub might actually be the future.

Cue Moggmania, the political social-media phenomenon of the summer. Young Conservatives celebrated his rugged Euroscepticism, confident backing of Brexit and rejection of the centrist policies offered by Theresa May. Meanwhile his views on women’s reproductive rights and gay marriage prompted liberal outrage as it became clear that his genteel and self-deprecating persona was the overlay for an entrenched social conservative whose views sometimes sound more in tune with the right of the Republican Party than the 21st-century Tory party.

Such is the man who has cleared his diary to have lunch with the Financial Times, a paper he has read since he was a young child to guide a strategy that started with a £50 punt on the stock market at the age of eight — and developed into an investment business with $8.5bn under management, mainly in emerging markets.

As fellow diners take their seats, glancing at the distinctive figure sitting at the window, the Eton- and Oxford-educated MP laughs off recent speculations about his prime ministerial chances. “I don’t take it much more seriously than I take myself. It’s all good fun but it was summer froth.” He adds: “I’m a quiet West Country politician who has been of a little interest over the summer. I wouldn’t put it any higher than that.”

I remind him that he once said that he wanted to be “a millionaire at 20, a multi-millionaire at 40 and prime minister at 70, when I’ve made enough money to afford to waste some on politics”. It seems to be going to plan so far, I suggest. Rees-Mogg throws his head back and gives a high-pitched laugh: “I think I said that when I was 11,” he says. Self-deprecation has ever been a powerful weapon in his armoury.

We sit and admire the views leading from the village of Chew Magna up to the sunlit slopes of the Mendip Hills, where his family has owned land for 400 years and where they for a while derived an income from investments in the now-defunct Somerset Coalfield.

Today, the MP for North East Somerset is apologetic: he has to attend a constituency meeting after lunch so will stick to water. “It’s appalling,” he says. “In the old days Lunch with the FT was a proper lunch: now it’s people eating a stick of celery.” Under moderate duress, he agrees to join me in half a Butcombe ale. “I’m not a great beer drinker but I do like Butcombe, probably because it’s made of good Somerset water.”

I guess that his culinary tastes might veer to the traditional, a view reinforced by his celebration of the salted butter. “Unsalted butter is a sin against the Holy Ghost,” he exclaims. Too continental for his tastes? “You said it,” he laughs.

Rees-Mogg, who was recently criticised for saying that it was “rather uplifting” to see volunteers helping out at food banks for the poor, goes for the mackerel pâté on an oat waffle with apple, followed by a 10oz rib-eye steak (rare) with oxheart and hand-cut chips. He waves aside the red cabbage and I wonder if he is not especially fond of vegetables. “I like some vegetables,” he insists. “I very much like potatoes.”

Like many picturesque drinking holes in the rural south-west, the Pony and Trap has reinvented itself as a high-class gastro-pub; brother and sister Josh and Holly Eggleton’s restaurant has held a Michelin star since 2011. I opt for mussels and cockles in cider and plaice with shrimp.

Rees-Mogg’s constituency of small towns and villages only voted narrowly for Brexit in last year’s referendum, but his boundless enthusiasm for leaving the EU has endeared him to grassroots Tory members; he will be a star attraction on the fringe of next week’s party conference in Manchester. However, his hardline Brexit views put him increasingly at odds with Mrs May, who just eight days ago effectively put Brexit on hold until 2021 in a speech in Florence.

“It’s not a big betrayal but I can’t pretend I’m enthusiastic about the prime minister’s speech,” he says, with studied restraint. He is especially sceptical of May’s decision to put €20bn on the table as an opening offer in the dispute about a British “divorce settlement”.

“I would have been more careful about the money side of it,” he says. “Money is our best card — we’ve got it and they need it. I would have been more cautious in making promises that will now be cashed in.” He is also worried about a proposed two-year extension of free movement, beyond the formal Brexit date of March 2019.

It would be “the worst of all worlds”, he says, if Britain entered a transitional arrangement after Brexit and was still subject to the rulings of EU judges in Luxembourg, yet that appears to be what May has in mind. “That’s my absolute bottom line,” he says. “If there’s any backing down on the ECJ point then we’re not actually leaving.”

His enthusiasm for Brexit is primarily about restoring full sovereignty to Westminster. “The one thing I love about Brexit is that the politicians here are now responsible,” he says, between mouthfuls of mackerel pâté. “We can’t blame anyone else, we can’t say it’s Johnny Foreigner’s fault.”

Does he fear May will fail to deliver a good Brexit? “Mrs May is absolutely brilliant and will do a fabulous job,” he says with a blazing sincerity that suggests a bust-up may not be far away. He says he is not sure how he will celebrate “independence day” but suspects there will be a party with bunting to which I will be invited. The joyous prospect is complemented by the more immediate pleasure of the stew of delicious cockles, immaculately drowned in cider.

As we finish our starters, I observe that Rees-Mogg has until now been seen primarily as an impeccably mannered toff who brought some levity to politics. His good-humoured campaigning in the tough Labour heartlands of central Fife in Scotland, nanny in tow, first brought him to national attention in 1997. The son of William Rees-Mogg, a former Times editor, he had a gilded education before heading off to work in the City of London and Hong Kong and eventually setting up his own company, Somerset Capital Management. He lives with his wife Helena de Chair at the 400-year-old Gournay Court, just down the road.

His use of floccinaucinihilipilification earned him the record for the longest word uttered by an MP on the floor of the House of Commons, while his steadfast refusal to embrace the 20th century, let alone the 21st, earned him a cult following, even among opposition MPs, who appreciated his seriousness as a backbench parliamentarian. He is an assiduous attender of debates, sometimes stretching out full-length on the green leather benches while waiting for his turn to speak. His dry humour, courtesy and eloquence had him marked down by some colleagues as a future Speaker of the Commons.

I ask him about the story that his nanny, Veronica Crook, once stood behind him at Glyndebourne to shield him from the sun. “Nanny very briefly did, but as a joke,” he says, finishing off the mackerel. Earlier this year he admitted to never having changed a nappy — why not? “Nanny would kill me! She’s very protective of her charges.” Crook raised the young Jacob and now — after more than 50 years of service to the family — looks after his six children. Rees-Mogg professes to have never cooked or washed up in his life.

All this was seen as very droll. Yet as social-media campaigns such as the Jacob Rees-Mogg Appreciation Society, Can’t Clog the Mogg and Ready for Rees-Mogg proliferated over the summer, there was a sharp reappraisal of the Tory MP by the liberal media and Labour opponents: was it time to start taking him seriously?

For a few weeks profile writers linked his name to the global populist narrative of Bernie Sanders, Donald Trump and Jeremy Corbyn. A 24-year-old man from the South Yorkshire town of Doncaster had the word “Moggmentum” tattooed on his chest, a reference to the grassroots Momentum campaign that helped the left-winger Jeremy Corbyn become Labour leader two years ago. If the two share anything, it is perceived “authenticity” in an age when the centre has lost the confidence of the public. One survey of Conservative party members this month found Rees-Mogg was their favourite to succeed Mrs May.

Rees-Mogg’s supposed authenticity and rise to celebrity mirror those of Boris Johnson, another eccentric rightwing former Eton and Oxford alumnus. It is no coincidence both were successful panellists on satirical news show Have I Got News For You. “It’s quite flattering to be asked on,” Rees-Mogg says. “Then I get there and I don’t understand a word they’re talking about so I just blink and in that way I stay out of trouble.”

Many struggled to take Johnson seriously until he became the face of Brexit, using his celebrity to galvanise the campaign. They are not making that mistake now. Matthew Parris, a former Tory MP, wrote in the Times: “Mr Rees-Mogg is more than a possible leadership contender: he and his claques are in contention for the soul of the Conservative party. Unless what he represents is confounded, conservatism’s future as a unified political force is in peril.” He added: “For the 21st-century Conservative party, Jacob Rees-Mogg would be pure hemlock. His manners are perfumed but his opinions are poison. Rees-Mogg is quite simply an unfailing, unbending, unrelenting reactionary.”

Suzanne Moore in the Guardian drew comparisons between Rees-Mogg and Johnson, Trump and Ukip leader Nigel Farage, with their “veneer of authenticity; an ability to cut through perceived liberal wisdom; and enormous privilege that is flaunted, rather than hidden”.

Rees-Mogg welcomes the arrival of his steak with a smile. “One of the joys of life is winding up po-faced lefties,” he says. The comparisons with Johnson are inexact: Rees-Mogg possesses principles to which he generally adheres. But he admits that this summer he has had a degree of scrutiny to which he has never previously been exposed.

He faced questions again about why in 2013 he addressed the annual dinner of the Traditional Britain Group, which had called for ethnic minority Britons to be “requested to return to their natural homelands”. He says his attendance at the event was a “dreadful mistake”. The left criticised him for his small-state conservatism, but he says his time campaigning in the council estates of Fife reinforced his view that the state was often the problem not the solution. “The safety net had become a trap,” he says.

Meanwhile he came under the fiercest criticism for his social conservatism. He declared in a television interview that — as a Roman Catholic — he disagreed with same-sex marriages and opposed abortion, including in cases of rape. He says he felt he should answer the question “as straightforwardly as I could” but admits: “It’s very easy for the Catholic church to appear dogmatic. Mercy is an important part of the church’s teaching,” he adds. “Everything you say has to be tempered with mercy.” He believes that life begins at conception but is “sometimes taken”. “Then God has mercy. One should always remember that the mercy of God is very great.”

If he ever held high office, would he try to impose his views on others? He says not and that, in any event, issues such as abortion were always deemed to be matters of conscience for individual MPs: “I’m not seeking to recreate Iran in the United Kingdom.”

As he talks, Rees-Mogg is assiduously removing all evidence of greenery from his plate. “I never eat salad — horrible stuff,” he says. “I’m not a rabbit.” At home his diet sounds hardly any more balanced. He says he tends to eat what the children are having. “There’s nothing wrong with a good, honest fish finger,” he says. “Or ham, egg and chips.”

The Rees-Mogg steak is deemed excellent and the chips admirably chunky, while my plaice is succulent, although only accessible through a dense tangle of seaweed. I polish off mine, but he leaves hunks of steak on the side of the plate: “We’re going out for dinner later,” he explains.

We finish where we began. As the coffees arrive — espresso for me, Americano for him — I ask him whether he would like to be prime minister. “I don’t think ‘like’ is the right term,” he says. “I don’t think prime ministers ought to like being prime minister: it should be a question of duty.” What if the call came from an anxious nation? “It won’t.”

He notes that there has never been a prime minister who has reached the highest office without having first served as a minister. He says that even the prospect of joining May’s government seems unlikely, given that when asked recently if Rees-Mogg would be promoted, the prime minister “giggled”.

But surely the thought must be in his mind? After all, it’s not every day a 24-year-old tattoos the word Moggmentum on their chest. “He did it for a bit of a laugh,” Rees-Mogg says. “I asked him what would happen if he changed his politics.” Is he any closer to entering the 21st century? Does he use Uber? No. Can he name any pop groups? Not really.

Rees-Mogg, a staunch monarchist who changed the last four digits of his phone number to 1649 to commemorate the death of Charles I, has to go. His constituency calls. I ask him whether this whole fogeyish thing is an act. “Funnily enough, people asked the same thing at Eton. They said, ‘You can’t really be like that.’ I just am. The most definitive answer I can give is that nobody would deliberately develop my image.”

There is a pause in the car park. The man seen by some as the future of the Conservative party contemplates how to get into his 1968 Bentley T-Series before cracking the conundrum. “George!” he calls out with delight. “This shows how safe Somerset is — I left the keys in the ignition!”

George Parker is the FT’s political editor

Illustration by James Ferguson