Bill Browder sits in his London home-office answering incessant phone calls. The walls are festooned with paintings he bought during his time in Russia as its biggest foreign investor and hedge-fund tycoon, before being summarily expelled in 2005.

Browder, 59, who says he is ethnically Jewish though not religious, maintains an ironic sense of humour in the face of what he says is a suddenly increased threat to his own life.

“Yes, I suppose I am Putin’s public enemy number one outside Russia and Ukraine,” he tells the JC. “And the dangers for people like me have increased a lot after the murder of Alexei Navalny. Navalny was the biggest and most important critic of Putin, and Putin showed no worry about killing him. That means he calculated that there is no consequence.

“Putin has lost all restraints. He will embark on an international killing spree and that includes people in the UK. Including people like myself.”

Letters from the Gulag: Alexei Navalny, in Moscow in 2019, before his poisoning and final imprisonment (Photo by Dimitar Dilkoff/AFP via Getty Images)

Even in the days when his good relationship with Putin and his cronies were coming to an end, Browder says he could see dangers looming. He began driving in a three-car convoy around Moscow, and always carried £5,000 in his briefcase to bribe Russian border guards if the tables were suddenly turned on him.

Now, Browder, who abandoned his US citizenship and became British in 1998, says he is taking precautions in London, but declines to elaborate –understandably. It is impossible not to think of the horrors that have befallen Putin’s enemies, from novichok poisoning to being blown up in a plane.

“I have to live for the moment, as you never know when my life comes to an end,” he remarks matter-of-factly.

However, he says: “Navalny’s death has energised me and others to step up further our fight for justice.” He is calling on Western governments to help get one of his closest friends out of a Russian jail, but knows this is looking increasingly unlikely.

However he also sees some signs of hope. For one thing, he says, Navalny’s widow Yulia has become a “petrifying” threat to Putin. “All of a sudden, she is a very wounded and angry woman with an extremely compelling profile - like her late husband. The story is nowhere near over – and Putin will probably regret killing Alexei.

“Putin is already ultra-rich but his focus now is purely on one thing: survival. He is not a politician – just a murderous thug. And such people often underestimate their enemies.”

He admits that inside Russia, Putin is firmly ensconced through intimidation, but says for every one demonstrator arrested laying flowers, there are 10,000 angry Russians fulminating in their kitchens – “and some time in the future this is going to explode in Putin’s face”.

Browder has a remarkable background. Photos and posters of Stalin, Lenin and Mao adorned the walls of his paternal grandparents’ home in New York state. His grandfather, Earl, who grew up in a very poor Protestant household, spent several years from 1927 in the Soviet Union as an ardent supporter of the Bolsheviks.

While there, Earl married a Jewish woman from Kaliningrad, Raisa. It turns out she had previously been married to the editor of the official Communist Party organ, Pravda – before the editor was assassinated by Stalin’s mass-murdering secret police.

Earl and possibly Raisa are revealed in British-American wartime papers to have recruited spies inside the USA for the Stalin regime. “Comrade” Earl led the US Communist Party for more than a decade before the Second World War, appearing as a presidential candidate on the cover of Time magazine.

Browder’s mother, Eva, was a Jewish refugee. In 1938 her own mother, in what Bill describes as “an act of huge love and self-sacrifice”, had sent her aged eight on a lonely sea voyage to America, where she was adopted. Browder’s maternal grandmother later managed to flee to the UK, and was reunited with her daughter in the USA years later.

Bill and his two brothers grew up in an atheist but not Communist home. His father and both uncles became renowned mathematics professors in Ivy League universities.

Probably rebelling against his hard-left background, Bill became a free-wheeling capitalist, yet was still fascinated by the Soviet Union and Russia. When Russia started its sell-off of major previously state-owned companies in the 1990s, Bill saw big opportunities to make big bucks. At one stage his own company was dealing in Western investments in Russia estimated at $4.5 billion.

Browder’s unequalled inside knowledge of Russian financial chicanery has helped him unmask the illicit wealth of a number of Russian billionaires. In that process, Browder’s lawyer and good friend Sergei Magnitsky was locked up on bogus charges and suddenly died in pre-trial detention after 11 months. Despite tall odds, Browder managed to persuade the USA, followed by several European nations, to pass legislation that has made it far easier to prosecute those aiding and abetting illicit Russian funds.

Browder’s biggest contribution, however, may be yet to come – to finally convince the UK and other countries to hand to Ukraine Russian state assets frozen in 2022 and worth an estimated $300bn. Browder believes Britain holds around $25bn.

“[Foreign Secretary Lord] Cameron has been talking about taking the plunge lately,” says Browder. “But we’ve faced conservative thinking and resistance from governments worldwide. Now with Navalny’s death, they look like finally doing it.”

Handing over the money for the Ukraine war effort could, Browder argues, lead to Russian defeat. “It would have a huge impact. Putin’s original intent was to become ultra-rich. He and his cronies stole a trillion dollars from Russian people. Then he started a war to divert attention from his theft.

“He knows if he loses the war he loses his position and he probably loses his life, like Gaddafi – killed in a ditch or with a bayonet through his head.”

Browder comes up with a last back-handed ‘compliment’ for the man who wants him dead. “I don’t think he is antisemitic as such. He is just anti-human. He is an equal-opportunity killer.”