The billionaire taking on the Brexiteers

But Soros (87) has a flair for political intervention. He revealed his support for Best for Britain at a dinner at his London home last week, at which he encouraged others to follow his lead. As Theresa May's government wobbles and teeters, he had decided it was time for the great clanking armaments of anti-Brexit forces to mobilise.

Behind that £400,000 lies potentially millions more ready to be deployed in restoring the UK to the EU.

Soros holds an unusual place in the nightmares of Tory governments. In 1992 he identified the weakness of Britain's position in the Exchange Rate Mechanism, the precursor to the single currency. He saw that John Major and his Chancellor, Norman Lamont, could not keep propping up the value of the pound for ever. At some point, they would buckle.

Soros ordered his traders to "go for the jugular" and made a billion pounds betting against the Bank of England and sterling. It was a traumatic event, closely witnessed by Lamont's then special adviser, David Cameron.

Some might see a paradox here, in the man who helped bundle Britain out of the ERM now agitating for it to reverse its vote to leave the EU. But for Soros, 1992 was an instance of cold-blooded capitalism, a knife in the throat of an indecisive government.

In the 25 years since his best-known smash-and-grab, he has gone from shadowy financier to global statesman, a committed foe of demagogues and autocrats and creator of Open Society Foundations, the second-largest philanthropic organisation in the United States after the Bill and Melinda Gates Foundation. So far he has endowed it with $32bn of his own money.

At Davos last month, on the same day President Trump touched down in his seven-helicopter convoy, Soros gave a speech arguing that we are living through a "revolutionary period" comparable to the fall of the Soviet Empire.

He said that the threat of nuclear war is suddenly very real again. He accused monopolistic IT platforms such as Google and Facebook of suffocating innovation and corrupting both public discourse and young minds. And he warned that nationalism had replaced the creed of "international governance and co-operation".

After the financial crisis of 2008, he said, the EU had lost support. "What had been a voluntary association of equal states was converted into a relationship between creditors and debtors where the debtors couldn't meet their obligations and the creditors set the conditions that the debtors had to meet. That association was neither voluntary nor equal."

He proposed root-and-branch reform to give countries more flexibility in their relationship with the EU. Otherwise, he feared, parties hostile to Europe would only grow more powerful across the continent.

Shortly before the Brexit vote, he said he hoped that Britain would stay in the EU for political as well as economic reasons. The EU was stronger with Britain in.

Soros's concern for the UK is rooted in his education. In 1947, when he was 17, he left Hungary, where he was born and had survived the war, for London. His father had obtained false identity papers for him. Soros worked as a busboy and railway porter to save money for his education and would sometimes stand at Speakers' Corner lecturing about the virtues of internationalism in Esperanto. His father, a committed internationalist, had taught him the language.

Eventually, Soros was accepted by the London School of Economics, where he studied under the political philosopher Sir Karl Popper. Popper's book, The Open Society and Its Enemies, would inspire the name of Soros's Open Society Foundations, a collection of organisations that have promoted democracy and human rights in 140 countries over the past 35 years.

The money for all the philanthropy came from Soros's remarkable record as a money manager. He opened his own fund, Quantum, in 1969 with a mere $6m. Using the most innovative forms of financial instruments and leverage, he built Quantum into a multi-billion-dollar behemoth, becoming one of the richest men in the world.

The size of the risks he took, he said, would make him weak with stress. His son Robert once joked there was more instinct than science to his father's investing: he bought when his back felt good and sold when it hurt.

Soros himself attributed his stomach for risk to his experiences in the war. In 1944, his father obtained false papers for the family to hide the fact they were Jews. This taught him to stare down even the harshest realities in search of a solution.

"Once you are aware of the dangers, your chances of survival are much better if you take some risks than if you meekly follow the crowd," he has said.

"That is why I trained myself to look at the dark side. It has served me well in the financial markets and it is guiding me now in my political philanthropy. As long as I can find a winning strategy, I don't give up. In danger lies opportunity. It's always darkest before dawn."

As Soros has got older, his role as an investor has changed - sometimes heavily involved, at other times not. The performance of his funds, though, is still closely followed. After Donald Trump's election last year they were reported to have lost $1bn on bets that the stock markets would fall on a Trump victory. His personal life has also evolved. Five years ago, on his 82nd birthday, he married for the third time, to Tamiko Bolton, then 40, founder of an online yoga business.

His political interests, though, have only intensified. In the US he was a supporter of President Reagan in the Eighties but then started giving money to the Democrats under Bill Clinton. He vigorously opposed President George W Bush and the wars in Iraq and Afghanistan. And in the most recent election cycle gave $16m to Democrat candidates. He was a strong supporter of Hillary Clinton and remains a vocal opponent of President Trump, whose election he said awakened "dark forces" in America.

He has also taken strong stands on a range of issues, supporting the regulation and taxation of marijuana, gay and lesbian rights, and groups fighting violent abuse by police. This has earned him the hatred of America's cable-TV Right.

In Europe, Soros has become a target for nationalist politicians from Vladimir Putin on down. Hungary's Prime Minister, Viktor Orban, who studied at Oxford on an Open Society scholarship, has funded a campaign against Soros, accusing him of arranging a massive influx of refugees into Europe. Posters have gone up with pictures of Soros, asking Hungarians not to let him "have the last laugh". In December, an MP from Orban's party posted a picture on Facebook of a burnt pig with 'This is Soros' carved into its flesh.

Soros has argued that Europe needs to do a better job of sending refugees to countries that want them, and where they want to be. Orban has accused him of trying to increase immigration at the expense of Europe's Christian culture. The campaign has struck many as a throwback to 1930s anti-Semitism.

The brickbats around Brexit might scare some. George Soros is unlikely to be one of them.