Arron Banks is the son-in-law of a Russian state official and his wife uses the numbers 007 in her email address. The family Range Rover’s numberplate was MI5 SPY.

Mr Banks’s pro-Brexit campaign was launched with funding from a prominent billionaire investor who originally made his fortune in Russia and went on to live on the Isle of Man, which is outside the European Union.

Mr Banks was in effect barred from working as a company director in Gibraltar after an investigation into his financial business there.

He is the honorary consul for the tiny Central American state of Belize, noted for its lively offshore registries. His Foreign and Commonwealth Office consular identity card states that his post is based at the “Honorary Consulate of Belize in Cardiff”. The address cannot be found in Google Maps. He is unlikely to be entitled to diplomatic immunity since sources say that honorary titles are exempt.

He accompanied Nigel Farage to Trump Tower in New York when the Ukip leader became the first British politician to meet the newly elected president.

Mr Banks was long ago described by a Westminster watcher as “the most obnoxious man in politics”, a heavily contested title which he would probably relish. He called Douglas Carswell, the former Ukip MP, “borderline autistic with mental illness wrapped in” although he later apologised for the cruel insult. He entitled his memoirs The Bad Boys of Brexit: Tales of Mischief, Mayhem & Guerilla Warfare in the EU Referendum Campaign.

Mr Banks has a penchant for capturing headlines by making bold claims that cannot always be seen to materialise. He first became prominent when it was reported that he was a Conservative donor who was going to give £100,000 to Ukip.

Lord Hague of Richmond, when he was foreign secretary, dismissed the defection saying that he was “not a senior figure in this party, not someone I know at all”. Mr Banks responded by claiming that he would increase his Ukip gift to £1 million. “He called me a nobody. Now he knows who I am,” a peeved Mr Banks told the media, who lapped it up.

Although it was reported that Mr Banks had given £250,000 to the Tories, the party disputed the figure. A search of Electoral Commission records did not show that he had given £1 million to Ukip. The Times asked him about the amount but he declined to respond.

Mr Banks set the media agenda when his organisation failed to be chosen as the official Brexit campaign group, a privilege that would have entitled it to spend £7 million, send out free leaflets and get referendum broadcasts. He threatened to delay the referendum by challenging the decision in the High Court. After a splurge of free publicity, he dropped the threat.

He was born on March 22, 1966, and grew up in Basingstoke. He is married to Ekaterina Paderina, the daughter of a Russian regional official from Ekaterinburg. Before her relationship with Mr Banks, she was briefly married to a retired British seaman twice her age, who fell in love with her after spotting her sunbathing topless in the Portsmouth constituency of the Liberal Democrat Mike Hancock, who was then chairman of the all-party Russia group. MI5 believed that the Kremlin was interested in the MP’s access to documents and contacts. Another young blonde Russian, who worked in Mr Hancock’s office, was ordered to leave Britain suspected of being a spy but she won an appeal to stay.

Not known

Ms Paderina, a linguist who appeared to have been trained in self-defence, met Mr Hancock as she sought his help to remain in Britain when her marriage was failing. The couple divorced after 18 months. Her ex-husband, Eric Butler, said: “She thought she was a Bond girl.” She told journalists in a light-hearted conversation at an awards ceremony: “I love Putin!”

Mr Banks’s reputed fortune, once estimated at £250 million, has been attributed to his work in the insurance industry. He agreed in 2013 not to apply to become a director at Gibraltar companies after an investigation by the authorities into the company he founded, Southern Rock, based in the offshore jurisdiction, about the amount of money held back by an insurance business to pay for claims. There was no admission of liability and he described the agreement as a “slap on the back of the wrists”.

He voluntarily recused himself from the register of the Financial Conduct Authority in London at the same time.

Mr Banks and Jim Mellon, a prominent investor who is sometimes described as Britain’s answer to Warren Buffett, both had in common that they bought shares in 2006 in an American telecoms business.

Mr Mellon, who first made his fortune in Russia after the collapse of communism, introduced Mr Banks to Nigel Farage. Leave.EU, the Brexit campaign group run by Mr Banks and fronted by Mr Farage, was reported to have received £100,000 from Mr Mellon.

Since Mr Mellon lived on the Isle of Man and had no vote in Britain, he would usually be barred as an overseas political donor but a glaring loophole in the referendum funding rules made his gift perfectly legal.

Regulations requiring individual donors to the referendum campaign to be on the British electoral roll only came into force on February 1, 2016, four months before the Brexit vote. Campaigns were entitled to set themselves up sooner.

Damian Collins MP said it was difficult to know if evidence by Mr Banks and Mr Wigmore to the parliamentary committee he chairs could be taken seriously

Mr Mellon became rich by investing in privatisation in Russia after the collapse of the Soviet Union. However, his asset management group Burnbrae explained: “Jim has not been involved in Russia or Russian investments since the 1990s, some 25 years ago, and when he was based in Hong Kong” and thus he was not influenced by Russia.

Mr Banks and Andy Wigmore, a former Belize diplomat who was head of communications for Leave.EU, met the Russian ambassador to Britain three times, and handed him the phone numbers for Donald Trump’s presidential transition team in November 2016. The Russian ambassador to Britain also tried to help to set up a deal for Mr Banks involving goldmines. Mr Banks has denied any wrongdoing in his relations with the ambassador.

Damian Collins, chairman of the digital, culture, media and sport committee, which questioned Mr Banks and Mr Wigmore, said they “put on the record that they frequently lie, exaggerate, misspeak and misunderstand. So it is difficult for the committee to know if we should take all of their answers seriously when it comes to data sharing and misuse, campaign spending, and their meetings with high-ranking Russian officials.”

Mr Banks told The Times: “Jim Mellon gave the money before rules kicked in. I have a Russian wife and a Russian father-in-law who I have never had any business dealings with.”