Katya Banks looked delighted to reach the pinnacle of British society as she strolled around the gardens at Buckingham Palace with her husband, the millionaire businessman Arron Banks.

Posing in a smart bronze jacket and matching hat, Katya seemed thrilled to be invited to the first of the Queen’s summer garden parties in May 2015.

Life for the Banks family was to get even better when Arron’s £8m donations to Leave causes helped secure the Brexit referendum result in June 2016.

Katya, 44, has since joined her husband on trips to Washington. Indeed, he was one of the first Britons to congratulate Donald Trump after his presidential triumph and was pictured alongside the billionaire in Trump Tower.

Now a Sunday Times investigation has uncovered the extraordinary story of how the attractive Russian came from nowhere to win a ringside seat to the two biggest political stories of the age.

Ekaterina Paderina, to use her maiden name, arrived in Britain in the 1990s to study marketing at Portsmouth University. The daughter of a senior Russian state official, she was swept up in a whirlwind romance with Eric Butler, a retired merchant seaman. The couple tied the knot in November 1998. Butler was 54, Paderina was 25.

The marriage soured within months. Soon after they met, friends of Butler say he was questioned twice by Special Branch, the secret police unit responsible for national security.

He filed for divorce in February 1999 and within months police were called when Paderina smashed a lamp over her husband’s head. She was charged with aggravated bodily harm. When asked by The Sunday Times, Banks said Paderina hit Butler “with a lampshade, very hard” but emphasised it was in “self-defence”.

“She was pregnant at the time of the alleged assault and her ex-husband was a 6ft-plus navy sailor,” Banks explained. “She was acquitted for obvious reasons.”

Friends of Butler, however, claim the case collapsed when the seaman refused to give evidence. They say Butler became concerned when Alexander Trifinov, a local Russian, allegedly threatened him on behalf of Paderina. At this point Butler decided to leave the UK.

Katya soon after she arrived in BritainKatya soon after she arrived in Britain
When The Sunday Times contacted Trifinov last week, he said: “Thanks to Mr Butler I did one week in jail.

“He said that I threatened him on behalf of Katya. I didn’t threaten him, I just put her up at my place for a few days. It was absolutely ridiculous. I was exonerated and so was Katya.”

Despite being cleared of all charges, the UK authorities served Paderina with a deportation notice. As a last resort she turned to Mike Hancock, the then local Liberal Democrat MP with a record of providing support to young Russian women. Later, when he was on the Commons defence select committee, Hancock had a four-year affair with another Ekaterina — Ekaterina Zatuliveter.

In 2010 the MP’s lover — then aged 25 — was arrested and accused of working for Russian intelligence. MI5 applied to deport her on grounds of national security but Zatuliveter won an appeal to stay.

Hancock, who was later thrown out of the Lib Dems for sexually harassing a female constituent, was attracted to Paderina’s cause. According to Trifinov, Hancock helped her to get a council flat.

“They were very good friends at one point,” he said. Hancock did not respond to a request for comment.

In October 2001 Paderina married Banks and moved to live with the businessman, 51, in his home north of Bristol.

No one can doubt Banks’s business acumen. The value of his insurance empire has soared with each passing year and he has also acquired five diamond mines in South Africa. His wealth has been estimated at £250m, although it is difficult to be certain as most of his companies are offshore.

Banks with Nigel Farage and Donald TrumpBanks with Nigel Farage and Donald Trump
He pumped £8m into the Leave campaign, described as the “single biggest donation to a political cause in British history”. Much of its populist anti-immigration message was mirrored in Trump’s election strategy.

Since the US president’s victory, however, he has come under mounting pressure over his campaign’s alleged collusion with Russia. Banks expects to be called to Washington to give evidence to the Senate into purported ties between the Kremlin, Brexit and team Trump.

Banks, who denies any links between Moscow and Brexit, has professed admiration for President Vladimir Putin, another supporter of Britain’s decision to leave the European Union. It is not known whether Banks’s respect for Russia pre-dates his relationship with Katya, who has given birth to three children since their marriage.

Her father, Evgeny Paderin, is described as “head of government property” in the Russian city of Yekaterinburg. Her email address contains the numbers 007 and she drives a Range Rover with the number plate MI5 SPY, although any suggestion that she has a deeper relationship with the Russian state prompts derision from the Banks camp, who say there is no evidence to support the allegation.

Katya maintained links with Portsmouth long after she left it. Butler, now 73, refused to be interviewed. But in a letter he sent to a friend in 2010 he claimed that his ex-wife had continued to enjoy the council flat in Portsmouth after she had moved to Bristol to live with Banks.

Butler had returned to Portsmouth in 2008 to find Katya still making use of the flat, a few hundred yards from the naval base — one of Britain’s largest military complexes.

The electoral roll shows her at the Portsmouth address under her maiden name, Paderina, while at the same time she was listed in Bristol as Mrs Banks.

Trifinov said she lived at the flat “for some time” and sometimes had “girlfriends from Russia staying there”.

Butler was furious. In the letter, seen by The Sunday Times, he claims he informed Portsmouth city council. Elaine Baker, a former lord mayor of Portsmouth, said the matter had been quickly settled. “I believe it was paid off in cash,” she said.

Banks was happy to confirm it: “[Katya] took this flat . . . and then moved down to Thornbury. Someone said the flat should have been given back and there was a settlement with the council. But it was not a criminal matter.”

When asked if he had settled the dispute, Banks said: “I know you journalists love conspiracy and the Russia-Trump is just gorgeous, but to be perfectly honest . . . I wouldn’t even remember money from last week, let alone that long ago.”