In 2011 Arron Banks floated Brightside, a Bristol-based insurance broker he had built from practically nothing. Unlike Banks, the new investors wanted to cash in, so the following year they unceremoniously sacked him as chief executive of the company and then in 2014 they sold Brightside to the private equity firm AnaCap for £130m.

Hours after his dismissal Banks, still fuming, went out to lunch with the firm’s commercial director, John Gannon, who had helped him start the business in 2005. In the car Gannon said how bad he felt. He explained how he’d had little choice but to go along with the decision. As they arrived at the Aztec Hotel and Spa, Gannon asked if there was anything he could do to make Banks feel better.

“I said, ‘There is one thing that will make me immediately feel better,’” Banks recalled recently. “‘All I want to do is hit you in the face.’ So he said, ‘Which way would you like me to turn my cheek?’ So he turns to the left and ‘bosh!’ – I hit him as hard as I could and he went over like a bag of cement.” The two men then ate lunch in silence as Gannon pressed an ice bag to his cheek.

Banks’s hunger for revenge did not stop there, however. Within six months he founded a new company, GoSkippy, and proceeded to poach Brightside’s best employees. He sent gloating emails to those former colleagues who had, he said, “stabbed me in the chest”. In one message he bragged: “Virtually all the sales team have left for Skippy – leaving the tea boy in charge.” In another he wrote: “You have no stats, no claims department, no rating engine and f*** all chance of persuading anyone to help create a new insurance vehicle.” In a third he said that being sacked “was like a pair of jump leads; it just fuelled the fires and the desire to show what can be done”. For good measure, after a series of claims and counterclaims, he won an out-of-court settlement from Brightside which cost his former company a few more million.

The saga says much about Banks, the man who subsequently deployed his fortune to campaign for Britain’s exit from the European Union. He is someone you cross or slight at your peril. Speaking on condition of anonymity, which is how most people chose to speak to me about Banks, an insurance industry expert said: “Arron is charming, charismatic and pretty popular in insurance circles. He’s great fun, but the thing about him is he’s very pugnacious. If he feels like you’ve crossed him he’ll come at you with all guns blazing.”

That is a lesson the Conservative hierarchy has also learned. Until 2014 Banks was a Tory party member and a modest donor. He then decided to defect to the UK Independence Party. Amid the pre-election hubbub of that autumn’s Tory conference, Ukip summoned political journalists to a press conference at Old Down Manor, on a Gloucestershire estate that Banks owns, to announce that he was giving it £100,000.

At that time the insurance magnate was hardly a household name, and the occasion was in danger of becoming an embarrassing non-event. But William Hague, the then leader of the House of Commons, inadvertently saved the day. He made the mistake of describing Banks in a radio interview as “somebody we haven’t heard of”. This, as Nigel Farage told me with a laugh, was probably true, because by then Banks had only donated to his constituency party. Banks was nonetheless incensed. He immediately upped his donation to £1m. Hague “called me nobody”, he told the journalists. “Now he knows who I am.”

As in the Brightside saga, Banks did not stop there. He claims to have pumped £7.5m into the Brexit campaign over the past year, most of it to Leave.EU, which is one of the two groups that championed Britain’s departure from the European Union in June’s referendum. That may well be the single biggest donation to a political cause in British history – and arguably it helped change the course of British history.

While most commentators focused on the official Vote Leave campaign and its high-profile political frontmen, such as Boris Johnson and Michael Gove, Leave.EU used social media to galvanise disgruntled blue-collar white voters of the north and Midlands. While Vote Leave concentrated primarily on the economic and sovereignty issues of interest to middle-class Tories, Leave.EU focused relentlessly, shamelessly and often outrageously on immigration. Much of its populist strategy was taken directly from the US presidential campaign of Donald Trump, a man with whom Banks feels such an affinity that his WhatsApp picture shows the two of them standing side by side, smiling at the camera and giving thumbs-up signs.

Few politicians or pundits are inclined to give Leave.EU much credit for Brexit’s victory, but there is a great deal of anecdotal evidence that the voters it targeted turned out in record numbers, and it is far from implausible to suggest that its campaign made all the difference in a very close contest. A senior official in the Leave camp – no friend of Banks – acknowledged that a combination of Leave.EU’s social media operation and Farage’s tub-thumping rallies “combined to connect with a large chunk of the blue-collar vote which ultimately proved absolutely critical to the result”.

Matthew Goodwin, a professor of politics at the University of Kent and co-author of Revolt on the Right, about the radical right in Britain, told me: “There’s an awkward attempt under way by those in Vote Leave to say, ‘We were responsible for the result. This had nothing to do with Ukip and Arron Banks, and if anything Vote Leave won in spite of the more hard-edged Eurosceptics.’ I completely disagree with that analysis.”

The vote set Britain on the road to Brexit but did much more than that. It shook a political establishment that Banks regards as self-serving, elitist and corrupt. David Cameron resigned, Labour sank into civil war, and in her speech to the Tory conference on 6 October, Prime Minister Theresa May sought to woo precisely the people who had been targeted by Leave.EU as she drastically repositioned her party.

But Banks is still not finished. He now plans to turn Leave.EU’s legions of supporters into an online “people’s movement”. He wants “to give voice to the forgotten millions of English people” who feel ignored by the political establishment, to an “England rising”. He intends to launch this latest quixotic venture early next year, and his goal is to ensure not only that Brexit – hard Brexit – is implemented in full, but to bring about deep reform of the system he so detests. “We can’t carry on with politics as normal,” he says. “It’s a disastrous state of affairs.”

“Don’t underestimate him,” Goodwin warns. “The fact he has a lot of resources, the fact he’s clearly willing to throw them into politics, and the fact he’s now got a track record of building networks and attracting a large database of registered supporters

means anything he does has to be taken seriously . . . My feeling is he’s ideally positioned to build something that could potentially have a very big impact on British politics.”

But just who is this maverick who has risen from obscurity over the past two years and used his wealth to exert a considerable, some would say alarming, degree of influence over our national life?

***

Banks’s driver, a burly former rugby player, collects me from Bristol Parkway Station in a sleek black BMW, but I soon discover that there’s nothing particularly grand about Banks. I walk into his second-floor office in a bland building on a nearby trading estate to find him wearing a T-shirt, shorts and trainers. He has been to the gym, he explains. He is 50 and needs to lose weight. He had a health scare in South Africa during the summer – a heart problem that required hospital treatment.

The office is light and spacious but unpretentious, save for a photograph of Banks shaking hands with the Prince of Wales at a Royal Commonwealth Society function. It was taken before he joined Ukip, he says with a grin. Before he became a pariah, in other words. On the windowsill is a book called 100 Good Things About the EU: between the covers, every page is blank.

As an ardent Remainer, I am expecting to dislike the man intensely, but I find him disarmingly humorous and frank. We chat for nearly four hours. Whether he is merely generous with his time, or loves the attention, I cannot tell.

He says he was born in Knutsford, Cheshire, and raised by his mother in Basingstoke, Hampshire, while his father managed sugar estates in various African countries – South Africa, Kenya, Somalia, Ghana – that they would visit for holidays. “He was awarded an OBE for services to sugar, which is more than I’ll ever get for services to Brexit,” Banks notes wryly.

At 13 he was sent to a “third-rate” boarding school, Crookham Court in Berkshire, which closed in 1989 after Esther Rantzen’s That’s Life programme exposed three of its teachers as paedophiles. He was never abused: he was too busy committing his own transgressions, getting expelled for an “accumulation of offences” that included selling lead filched from the roofs of school buildings. He accepts that his expulsion was entirely justified. It would have happened much earlier, he says, except that the struggling institution needed his fees.

He moved on to St Bartholomew’s in Newbury but was expelled again, this time for a “monumental pub crawl” that ended in a daredevil car stunt. His “lack of educational attainment” ruled out university, so he returned to Basingstoke, where he sold paintings, then vacuum cleaners, then houses. “I was quite good at persuading people to buy things they didn’t want to buy,” he says.

Inspired by Margaret Thatcher, he joined the Young Conservatives and sought election to Basingstoke Council for the Labour-held ward of Norden. He lost, despite buying a Labrador dog to broaden his appeal. He never ran for office again.

It was through the Young Conservatives that he met his first wife, Caroline, a teacher whom he married at 21. “Her parents really didn’t like me,” he recalls, laughing. “I think they wanted their daughter to marry a country solicitor or someone with prospects. When I asked her father [a dentist] if I could marry her he said, ‘No, you can’t.’ I remember writing him a stinking letter along the lines of ‘Who the hell do you think you are?’ which didn’t improve matters.”

A neighbour found him an entry-level job at Lloyd’s of London. He stayed seven years, rising to become a deputy underwriter before being recruited to run Norwich Union’s Bristol office. Later he worked as a consultant for Warren Buffett’s Berkshire Hathaway group. A framed $5 bill signed by Buffett hangs on his office wall, alongside a certificate for a single Berkshire Hathaway share that Banks bought for $83,000 a decade ago. It is now worth $216,000.

But Banks was no corporate man. He was too impatient, intolerant, unorthodox. “As I got older I realised there was no respite from stupidity,” he says, so he set up on his own. From a small office above a bakery in Thornbury, Gloucestershire, he launched MotorCycle Direct, which sold insurance to bikers over the phone. After two or three years he sold the firm for “a few million” and opened Commercial Vehicle Direct, which catered for White Van Man. “Within a very short period we were the largest van insurance company in the country,” he says. CVD duly morphed into Brightside, which expanded into multiple forms of insurance – life, cars, homes, travel, pets.

Today Banks owns a majority stake in Conister Bank on the Isle of Man, and several insurance-related businesses, some of which are based on the same island or in two other offshore tax havens: Gibraltar and the British Virgin Islands. But he makes no apologies. “I don’t give a monkey’s. I live in England. I pay tax in England . . . My position is: if you don’t like it change the law. Business people will always go for the most efficient thing.” He does little business outside the UK, and so will suffer little if Britain leaves the European single market.

At one point Gibraltar’s financial regulator ordered one of his companies, Southern Rock, which underwrites GoSkippy’s policies, to increase its reserves substantially in order to cover potential payouts. Banks responded as he so often does – aggressively. He threatened legal action. He also bought a full-page advertisement in the Telegraph attacking the regulator and PricewaterhouseCoopers, the accountancy firm; he accuses the regulator of having pressured PwC to exaggerate Southern Rock’s exposure.

Another curious incident involved a then 33-year-old female employee named Jo Featherby. The Sun reported that in 2012 Banks received an official warning from the police following claims that he had harassed her. Banks is unusually coy on the subject. He concedes he was given a warning, and that he settled Featherby’s claim for unfair dismissal out of court, but denies harassing her. He suggests he was merely trying to save her from a “pretty unpleasant boyfriend”, adding: “I probably intervened in something I should not have.”

His first marriage lasted ten years and produced two daughters, Charlotte and Sophie, both now in their twenties with Firsts from Exeter in history and bioscience. Charlotte works in marketing for the National Trust. Sophie, who opposed Brexit, is looking for her first job.

In 2001 he married again, this time to Ekaterina Paderina, known as Katya, a Russian from Yekaterinburg whom he met while attending a Britney Spears concert at the O2 Arena in London as the guest of an insurance

firm. Katya came to Britain in the 1990s to study marketing at Portsmouth University. She overstayed her visa but married Eric Butler, a merchant seaman who, at 54, was more than twice her age. The marriage ended within months, prompting officials to investigate whether it was a sham.

Years later the tabloids discovered that Michael Hancock, a disgraced former SDP/Liberal Democrat MP for Portsmouth with a history of assisting dubious young women from eastern Europe, had intervened to help Katya stay in the UK. That, plus her fluency in six languages and the fact that Yekaterinburg was once a closed city, led to suggestions that she was a spy. Banks responded by buying a personalised number plate for her Range Rover: X MI5 SPY.

Banks and Katya have raised three more children – Darren, 16, Olivia, 13, and Peter, 11 – who are all enrolled in expensive private schools (the older two board at King’s College, Taunton). “Why would I send them to a state school for a lousy education?” Banks says, when I ask how that squares with his leadership of the “People’s Movement”.

Sadly I did not meet Katya. She advertises herself on the website Model Mayhem as an aspiring actor: “I am fun and friendly with an extensive, glamorous wardrobe and a large house which could be used for location shoots. I will not do nudes.” And I had been repeatedly told how feisty she is, a description Banks cheerily confirms.

He recalls an occasion when they were guests in a corporate box at the Emirates Stadium when Arsenal played CSKA Moscow. Katya started cheering the Russians; the crowd below barracked her. She tried to climb out of the box to confront them, whereupon the stewards hauled her back and took her away for 30 minutes to cool off.

At one point the couple separated for a year. “We’re both quite eclectic, high-energy people and probably needed a break,” he says. “I was sent to the dog kennel for a period of time . . . In the end, we got bored of the divorce and legal bills and decided to give it a miss. You get so angry with the lawyer that it actually brings you together.”

By 2014, the year he defected to Ukip, Banks was riding high. He was worth more than £100m. Besides his insurance businesses, he had acquired five diamond mines – three that once belonged to De Beers in Kimberley, South Africa, and two in Lesotho. He had bought Old Down Manor from the Tubular Bells musician Mike Oldfield and transformed it into a wedding venue. He lived in a handsome stone house in the nearby village of Tockington (where a huge Union Jack flutters above the front lawn), and had another fine home overlooking a game reserve near Pretoria in South Africa. Oscar Pistorius was a neighbour.

He played hard. He owned racehorses. He went to Wimbledon each year and once played Virginia Wade at Queens at a corporate event, winning not a single game. He enjoyed squash, golf and shooting, and had run the London Marathon. He was a member of the RAC club in Pall Mall.

He was also charitable. He had competed in the East African Safari Classic Rally to raise money for Sentebale, Prince Harry’s children’s fund in Lesotho, distributing footballs bearing anti-Aids messages to schoolchildren en route. He had helped build a paediatric hospital in Belize and founded Love Saves the Day, a charity that finances microprojects for Lesotho women. Banks had also given nearly £200,000 to his local Conservative Association – £25,000 in cash and the rest a loan to enable it to buy its premises in Thornbury.

All of which prompts the question: why did he suddenly round on the Tories?

***

Banks cites his growing aversion to a Tory government led by Old Etonians which was presiding over a deepening gulf between Britain’s haves and have-nots.

“I hate Cameron – viscerally,” he says. “He was smart enough to get a first-class degree in politics and economics at Oxford University, and stupid enough not to realise the damage his policies were doing. Under his government the national debt doubled, interest rates collapsed to zero, the Sunday Times Rich List doubled or quadrupled and the average person’s wages flatlined. His economic policies were unacceptable.

“Cameron stuck in my throat because he was privileged in every possible way but too stupid to understand he should have been trying to help those who needed help.”

When I suggest that a man of his wealth makes an unlikely champion of the struggling working man, Banks retorts: “If you’re saying I should be poor to appreciate [the working man’s plight] I think that’s arrant nonsense.” His own paternal grandfather was a miner, he says. And he insists that he abhors inequality. He favours a near-100 per cent tax on inheritances of more than £5m.

His many critics offer other explanations. A disaffected Ukip ex-official says of his defection: “If you put up a poster saying ‘Look at Me’ outside the Odeon in Leicester Square you could not have made a bigger egotistical statement.” A senior figure in the Leave camp reckons that Banks – a provincial, self-made man who went to the wrong school and missed out on university – has “chips on both shoulders”, and that Hague’s put-down “was one of the most wounding things he could have said about [him]. Everything since that day has been about Banks trying to prove he’s a somebody.”

Others suggest that he had become, by his own admission, a “bored multimillionaire”, and simply saw an opportunity to make trouble and have some fun. “He loves to be mischievous, to upset the apple cart, to be a rebel – the boy who blows raspberries in front of the headmaster,” said a source who worked with him during the referendum.

The opportunity certainly existed in 2014. Ukip had won the elections to the European Parliament that May. Two Conservative MPs, Douglas Carswell and Mark Reckless, subsequently defected. The Tories were panicking. “If you ever wanted to jump into politics feet first and have an instant influence then Ukip was the place to do it,” said another former Ukip official. “Farage would have offered him the world. Banks would have thought it was bloody exciting. The party was right at the centre of politics, making headlines and flying high, and he could be up in the cockpit.”

In Farage, moreover, Banks would have seen a kindred spirit – an irreverent, rebellious outsider like himself who was scorned by the political establishment. Their first meeting over lunch at the RAC was not a success. Banks had flu and Farage wasn’t allowed to smoke – not even in the garden. “I had a terrible row with the waiters,” Farage recalls. But thereafter they got on famously. They shared a hatred of the EU – Banks calls it a “closed shop of bankrupt countries” and Britain’s membership “a first-class ticket on the Titanic”. They disdained all forms of political correctness, and they drank together.

“Banks became part of Nigel’s privy council of lads, part of his drinking entourage. They were like a group of best friends with their own secret words and hand gestures and in-jokes,” said the former Ukip official, who recalls several epic drinking sessions. “They regard the politically correct, nannying, self-righteous, sanctimonious, holier-than-thou liberal establishment with contempt and never miss an opportunity to poke it in the eye,” said another source who worked with Banks on Brexit. “They behave like a bunch of schoolboys on a day out – not the Bullingdon Club, but the lower fourth from a Coventry comprehensive.”

Farage puts it slightly differently. Banks “hates political correctness and career politicians and hedgers and trimmers and dissemblers”, he told me. “He’s just enormous fun to be with. When he lets his hair down, boy, he has fun. It’s refreshing to meet someone who knows how to enjoy life as he certainly does in spades.”

***

On the face of it, the general election of 2015 was a huge disappointment for Ukip. With the help of Banks’s money, the party won nearly four million votes and 13 per cent of the total, but just a single seat in the Commons. Even Farage fell short in Thanet South. Soon afterwards Banks emailed Andrew Reid, Ukip’s treasurer, to suggest that he take over as chief executive because the party organisation was so chaotic. “I’m currently paid a million pounds a year. So you get a million-a-year CEO for free,” Banks wrote. His offer was declined.

But Ukip’s erosion of the core Labour vote had helped the Tories unexpectedly to win an outright majority, with the result that their coalition with the Liberal Democrats was finished. That robbed David Cameron of any excuse for reneging on the promise he had made in 2013 to hold an In/Out referendum on Europe – a promise designed to stall Ukip’s rise. “Four million votes only got us one manky MP,” Banks says, “but it got us what we really wanted, which was the referendum.”

That July, Banks and his long-standing wingman, Andy Wigmore, took Farage off to Belize for a break. Wigmore is another colourful member of the Banks entourage – a naturalised Belizian who serves as trade and industry counsellor at the Belize High Commission in London and represented his country in trap shooting at the Commonwealth Games in Glasgow (he came last).

The three men stayed at Francis Ford Copolla’s Turtle Inn resort and went deep sea fishing, catching an eight-foot bull shark. They had a night of hard drinking in San Pedro on Ambergris Caye with Michael Ashcroft, the disaffected Tory peer who has extensive business interests in Belize. They also resolved to start preparing immediately for the referendum campaign, though Cameron had not yet set a date, and to create Leave.EU, which Banks would bankroll.

“He’s shown himself to be someone who doesn’t rush into things,” Farage says of Banks. “He thinks and talks, but once he’s made up his mind he goes for it in no uncertain way.”

Banks engaged the Washington campaign strategy firm Goddard Gunster to advise Leave.EU; it swiftly identified immigration as the critical issue and told him how to exploit it. As Banks recalled in the week after the referendum victory: “What they said early on was, ‘Facts don’t work,’ and that’s it. The Remain campaign featured fact, fact, fact, fact, fact. It just doesn’t work. You have got to connect with people emotionally. It’s the Trump success.”

He also employed Cambridge Analytica, another US company with several high-profile Republican clients, which explained the dark arts of targeted voter messaging. And he met members of Donald Trump’s fledgling presidential bid whose advice provided the bedrock for the Leave.EU campaign: don’t advertise – use social media and be outrageous, because, as Andy Wigmore put it: “The more outrageous you are, the more attention you get.” The result was indeed, by British standards, an egregiously outrageous campaign.

It began with a vicious battle for recognition between Vote Leave and Leave.EU – or rather with Grassroots Out, the umbrella organisation of which Leave.EU was the biggest component. Banks considered Vote Leave an elitist, out-of-touch Tory cartel and nicknamed its chief executive, Matthew Elliott, “Lord Elliott of Loserville”. When Carswell, Ukip’s only surviving MP, sided with Vote Leave, Banks infamously denounced him as “borderline autistic with mental illness wrapped in”.

For its part, Vote Leave considered Ukip and Farage toxic and found the focus on ­immigration distasteful. “The Tory posh boys saw the referendum as theirs to run. They would not discuss the issues we felt would excite the general British public . . . They wanted nothing to do with Ukip or me,” Farage told me with a chuckle.

***

Banks was furious when the Electoral Commission designated Vote Leave the official voice of the Out side, allowing it to spend £7m in the immediate run-up to the referendum and guaranteeing it free airtime. He threatened legal action, but reconsidered when told this could delay the vote.

Thereafter Leave.EU became, in Banks’s words, “the provisional wing of the Leave campaign”. Operating mainly from his offices in Bristol, it pumped out a stream of videos, cartoons, text messages and “news” clips which it posted on Facebook, Twitter, YouTube and other social media platforms.

Much of the comment was inflammatory, if not downright xenophobic. “Are you concerned about the amount of crime being committed in the UK by foreign criminals?” asked one video. “Are you worried about the overcrowding of the UK and the burden on the NHS?” another said. One tweet proclaimed: “Islamic extremism is a real threat to our way of life. Act now before we see an Orlando-style atrocity here,” referring to the deadly attack on a Florida nightclub by an Afghan American on 12 June.

Other messages were disingenuous at best. “Dave wants to give 75m Turks access to your #NHS!” said one, even though there is zero chance of Turkey joining the EU in the foreseeable future. Another quoted Victoria Beckham’s criticism of the EU without mentioning that it was 20 years old. Yet another cited General Sir Mike Jackson’s doubts about the EU but failed to mention that they came from a newspaper article in which he came down in favour of Britain’s continued membership. “We used their own words but picked the bits we wanted,” Banks says. He laughs as he recalls how he ordered a Leave.EU employee who had apologised to the furious general to call Jackson back and “unapologise”.

On occasion Leave.EU went too far even for Farage. In one video promoted by the group, Donald Trump likened Muslim immigrants to a snake that bites a kindly woman who seeks to help it – clearly implying that some immigrants were terrorists. “I wasn’t overly keen on that,” Farage told me. When Farage was excluded from the BBC’s Wembley debate, held two days before the vote, Leave.EU published the mobile-phone numbers of BBC executives and urged its followers to call them. “Nigel bollocked me for that,” Banks confesses. Following the murder of the pro-Remain Labour MP Jo Cox on 16 June, Banks commissioned an instant poll to gauge the effect – a move widely seen as distasteful.

“We picked fights with just about everyone,” Banks says, but the more the mainstream media and politicians fulminated at Leave.EU’s antics, the more they drew attention to its message. From Trump, “We learned how to use and abuse the mainstream media with their phoney outrage,” Banks says. “We fed off that fake outrage. All they were doing was giving us more ­oxygen . . . The mainstream media did more to grow our reach than anything else.”

Leave.EU claims that in some weeks it reached as many as 15 million people. One video was viewed 9.3 million times on Facebook. Several were watched more than a million times. Whenever someone “liked” or commented on one he or she was swiftly contacted by Leave.EU’s 70-strong call centre, also housed in the Bristol offices, and invited to join the cause. The Westminster bubble “never understood the power of the beast”, Banks says. “If Vote Leave had run the campaign without Nigel, Ukip and what we did, they’d have lost it hands down.”

The two Leave campaigns certainly dovetailed, albeit inadvertently. Vote Leave courted Tory Eurosceptics from the affluent shires. Leave.EU galvanised poorer, less educated, socially conservative voters in deprived parts of the country that Vote Leave could never hope to reach. Farage says Leave.EU was “largely responsible for finding them, contacting them and reaching out to them, using social media in a way no one in British politics has ever done before”.

Banks has no scruples about the tone or style of the Leave.EU campaign. “Politics is a dirty business,” he says. Indeed, he has written a soon-to-be-published book about the referendum that is gleefully entitled The Bad Boys of Brexit: Tales of Mischief, Mayhem and Guerrilla Warfare in the EU Referendum Campaign. His co-author is Isabel Oakeshott, the journalist who retailed the hotly disputed story, published in another recent book, about Cameron performing a lewd act on a dead pig while at Oxford.

“We always knew the referendum would come down to two things – the economy on the In side and immigration on the Out side, and that if you could keep the subject on immigration you would win,” Banks says. “What we would do was say things other people were thinking and not prepared to say and then not back down on it. We never back down on anything.”

Banks denies being racist. He claims to support immigration so long as it is controlled. But he does confess to being “tribal”, to feeling more affinity with our Anglo-Saxon “kith and kin” – Americans, Australians, New Zealanders and South Africans – than with other nationalities. “It’s part of a wider debate about: ‘Should we have our identity destroyed by this liberal globalism, or do we retain pride in our country and what we believe in?’”

He certainly does not apologise for using his substantial wealth to influence the vote. “It’s war,” he says. “If you don’t like it, change the rules. The In campaign was funded by Goldman Sachs, JPMorgan and a bunch of disreputable corporates. What’s worse?” And he argues: “Why shouldn’t I fight for what I believe in? To me it’s a matter of life and death for my country. We either get back control of our destiny or not.”

Nor does he hide the extent of Donald Trump’s influence on his campaigning style. He knows and likes Trump, saying he is “a lot more amiable and personable” in private. He also shares Trump’s contempt for the political establishment and mainstream media, and admires his ability to reach disaffected voters. Both Banks and Farage attended the Republican convention that nominated Trump in July. Banks was at the Mississippi rally on 24 August at which Farage endorsed Trump and he will attend the final presidential debate in Las Vegas on Wednesday. He thinks Trump will win in November, and would vote for him if he could, because Hillary Clinton “is a continuation of the failed policies of America”.

Banks shrugs off the uproar over Trump’s lewd comments about groping women which were caught on tape. “To a group of people they would probably be unacceptable. If you say them to a friend you know well as banter – so what?”

Does he share Trump’s admiration for Vladimir Putin? “I do in a way,” says Banks, who enjoyed a long, boozy lunch with the Russian ambassador to Britain at his residence during the referendum campaign. “He’s a nationalist, in the sense he’s trying to look after his country first and others second . . . I admire his strength as a politician but not necessarily all his policies.”

But Putin uses that strength to crush dissent, rig elections and close down the independent media, I point out. “You know as well as I do the words ‘independent media’ don’t mean anything,” Banks retorts. “Murdoch controls all of our terrestrial TV channels [sic], most of our newspapers . . . Maybe he [Putin] is just a bit more brutal in the way he does it.”

He suggests that the president’s military interventions in Ukraine and the Crimea were “a natural reaction to what the West has been doing . . .The Russians have their sphere of influence no different to the rest.” He even defends Russia’s robust military support for a Syrian regime that has used every conceivable barbarity against its own people. “The rebels and Isis are interchangeable,” he contends. “You have to be pragmatic. What’s more important – defeating Isis, or the civil war within Syria?”

At no point does he show any sympathy or understanding for the Syrian refugees who have sought refuge in Europe. Indeed, he defends Ukip’s highly controversial “Breaking Point” poster, showing a line of people queuing to move further north into the EU across the border between Slovenia and Croatia. Look at the picture closely, he says. “They are all young men in their twenties – economic migrants.”

Nor, for that matter, did he express any concern at the spate of anti-foreigner and racial attacks that followed the referendum, including one on a Polish cultural centre in Hammersmith, west London, on 26 June. “What’s a psok cultural centre [sic] when it’s

at home,” he tweeted. “Pack in the guardian connected outrage. Yawn . . .”

***

Last week, exactly two years after he defected to Ukip, Banks watched, bemused, as Theresa May delivered an establishment-bashing speech to the Tory party conference, courting the very constituency that Ukip and Leave.EU had targeted.

The Prime Minister called the referendum a “quiet revolution . . . in which millions of our fellow citizens stood up and said they were not prepared to be ignored any more”. She promised to champion “ordinary working-class people” not the “powerful and privileged”, to help those left behind by globalisation and to curb immigration. She berated those “politicians and commentators” who “find your patriotism distasteful, your concerns about immigration parochial, your views about crime illiberal”. It was “like watching Nigel in a skirt”, joked Banks, who backed Andrea Leadsom in the Tory leadership contest and does not believe May will deliver on her promises.

The previous day there had been another surprising development. Diane James resigned just 18 days after replacing Farage as Ukip’s leader, leaving Steven Woolfe as the favourite to succeed her. Then, last Thursday, Woolfe clashed with a fellow Ukip MEP and ended up in hospital in Strasbourg. Banks likes Woolfe, whom he regards as a credible and charismatic figure, with his northern working-class background, but acknowledges that “the Struggle in Strasbourg may well destroy him – he didn’t come out of it very well”.

Banks is now uncertain whether to continue funding Ukip, a party run by “a team of circus clowns”. Much depends, he says, on whether a viable leader emerges from the chaos: a leader capable of controlling the party and taking the battle to Labour. Theresa May has “frozen us out of the Tory side of the equation”, he says, but Ukip now has a “huge opportunity” in Labour’s heartlands because Jeremy Corbyn’s values “just don’t connect with the sort of blue-collar, socially conservative Labour people who voted for Mrs Thatcher”.

Yet Ukip is no longer the project that most enthuses him. Rather, it is his People’s Movement. Unusually, he and Farage disagree about this. Farage believes Banks should preserve the strong Leave.EU brand to fight for the full implementation of Brexit, sector by sector, but Banks has something far more ambitious in mind.

He wants to convert Leave.EU’s hundreds of thousands of followers into an online army, much like Beppe Grillo’s Five Star Movement in Italy, a force that transcends conventional party politics and the left-right divide. He envisages it as an exercise in direct democracy, a forum where people can post, debate and vote on ideas – and then embrace them in such numbers that politicians are compelled to respond.

The People’s Movement would not be linked to Ukip. It would work to ensure that Brexit is fully implemented, but it would also press for profound political reforms, such as replacing the House of Lords with an elected senate, halving the size of the Commons and introducing fixed terms for MPs. Banks is exploring other bold ideas – ideas that he hopes will appeal to voters of any party – such as replacing foreign aid with a form of service overseas for young Britons, working under the army’s auspices.

The old two-party system is an anachronism, he argues. “Our future lies in a different kind of politics, neither left nor right but radical. We believe there’s a great scope for an online movement that can embrace people from all across the political spectrum. There’s a change in the wind . . . Social media has transformed everything.”

Pie in the sky? Probably, but who knows? Banks is rich, resourceful and determined, and we live in extraordinary times, in which pundits and pollsters are repeatedly proved wrong and populist insurgencies are shaking political establishments across the Western world. Exploiting public discontent has seldom been easier.

Marine Le Pen of the Front National will be fighting for the French presidency next year. The populist right-wing Alternative für Deutschland will contest the federal elections in Germany. Geert Wilders’s Partij voor de Vrijheid (“Party for Freedom”) will be a strong contender in the Dutch general election. “Banks’s intervention should be seen against that backdrop,” Matthew Goodwin told me. “It’s where we are right now. It’s the zeitgeist.”

Martin Fletcher is an NS contributing writer