Every tsar has his personal demon, goes an old Russian saying. If so, the fiend stalking President Vladimir Putin is almost certainly Boris Berezovsky, the former Kremlin insider who claims to have placed Mr Putin on his throne and now publicly threatens to overthrow him.
Earlier this month, from exile in Britain, Mr Berezovsky told The Guardian he was working with forces 'close to the Kremlin' to prepare a coup d'etat that will sweep Putin away. 'We need to use force to change this regime,' said Mr Berezovsky, 61. 'It isn't possible to change this regime through democratic means. There can be no change without force, pressure.'
The Kremlin went ballistic. The Russian ambassador in London, Yury Fedotov, presented the British government with a warrant for Mr Berezovsky's arrest on charges of embezzlement and graft during the wild privatisations of Russian state assets in the 1990s. Mr Putin's spokesman, Dmitri Peskov said, 'We now expect British authorities to rethink their decision to harbour this fugitive billionaire.'
Moscow warned that Russian-British relations would suffer if Mr Berezovsky was not turned over, and, to drive the point home, dozens of Russian officials and business leaders abruptly cancelled plans to attend an annual economic forum in London. It did not help that Mr Berezovsky quickly qualified his remarks, insisting that he intended to use only 'non-violent means'.
At home, Mr Putin cracked down hard. Tiny mid-April street demonstrations by an anti-Putin coalition called The Other Russia, which denies any connection to Mr Berezovsky, were met with 9,000 helmeted riot troopers wielding truncheons and backed by armoured vehicles. About 200 were arrested, including the group's leader, chess grand master Garry Kasparov. 'The mask has come off the Putin police state,' Mr Kasparov said. 'It's obvious the regime is nervous and unstable if this is how they react to a non-violent march.'
After Mr Putin arrived in power seven years ago, he stripped Mr Berezovsky of his influence, as well as much of his property, and hounded him into British self-exile. Other former 'oligarchs', who lorded it over Russia during the chaotic '90s, received similar treatment. Under his newly adopted name, Platon Elenin, Mr Berezovsky today lives comfortably in a palatial, and heavily guarded, US$20 million, 70-hectare estate in Wentworth, Surrey, along with his wife, Yelena, and six children from three marriages. His fortune, estimated at US$3 billion by Forbes in 1999, is said to be half that today.
He appears to have few active business interests but maintains lavish offices in Mayfair, from where he denounces Mr Putin as a tyrant and lauds himself as a true liberal democrat to a steady stream of journalists, Russian emigres and other visitors. Most experts think Mr Berezovsky is washed up as a political force, an impotent and bitter blowhard, and no threat to the Kremlin. 'Berezovsky is incapable of doing anything,' says Moscow-based political scientist Leonid Radzhikhovsky. 'He's just useful for the authorities as someone to blame things on.'
So, it may seem astounding that a bit of bluster from a former Kremlin insider can provoke a near panic-stricken response from one of the world's most powerful states. Yet, this is no ordinary time in Russia. Mr Putin, who has largely recreated Russia's traditional autocratic system of one-man rule, insists he will walk away from the top job when his second term expires next March. Experts say this has prompted a ferocious power struggle among his inner circle, and, amid the infighting, some Kremlin groups worry that outside resources - such as financing from an exiled tycoon - might prove decisive in helping an opponent.
'Berezovsky is a master of provocation,' says Alexei Mukhin, director of the Centre for Political Information, an independent think-tank in Moscow. 'He is trying to ratchet up trouble, to exploit the strife that is growing within the upper elite.'
In few nations do rulers feel more vulnerable to an unpredictable shift in political weather than in Russia, where two mighty states, tsarist Russia and the Soviet Union, vanished into history's rubbish bin, along with their governments and social systems, in the past century. In recent years, a wave of 'coloured revolutions' in Georgia, Ukraine and Kyrgyzstan has similarly swept away leaders whose rule once looked as solid as Mr Putin's does.
'It's the logic of the system Putin has created to fear any opposition,' says Masha Lipman, of the Carnegie Centre in Moscow. 'It's only in a top-down, autocratic system where the threat of a palace coup becomes believable. Therefore, a few thousand people on the streets shouting oppositionist slogans makes them jittery. They can't afford to leave anything to chance.'
Mr Berezovsky's reputation - some say 'myth' - as the Machiavellian genius who manipulated Russian politics from behind the scenes during the 1990s clearly still carries weight. 'Berezovsky is one of the most important creators of the political system Russia has today,' says Ilya Ponomaryov, of the independent Institute of Globalisation Problems in Moscow. 'Exiled from his own creation, he finds himself driven into a campaign to destroy it.'
Born to Jewish parents in Moscow in 1946, Mr Berezovsky was educated as a mathematician and built a respectable Soviet career as a management specialist. As the USSR crumbled in the late '80s, he went into business, importing computer hardware and used cars from the west to resell at huge profits in still-closed Soviet markets.
Following communism's demise, his new company, LogoVaz, somehow gained control over Russia's biggest automaker, AvtoVAZ. In 1993, he raised US$50 million through a pyramid scheme, called AVVA, in which he promised to pay back investors with new cars, and used the cash to dabble in real estate, acquire media assets and move into bigger things.
In 1994, he barely survived one of several assassination attempts when a bomb detonated under his car, decapitating his driver and leaving him with third-degree burns.
A post-Soviet Russia run by then-president Boris Yeltsin, who died last week, provided vast opportunities for self-enrichment to those with the president's ear. Many of Russia's economic crown jewels, including oil, metals, telecommunications and forest industries were privatised, often in rigged auctions arranged by Kremlin insiders, on the legal strength of nothing more than a decree signed by Yeltsin.
'Russia under Yeltsin was pure chaos,' says Gennady Chufrin, deputy director of the official Institute of World Economy and International Relations in Moscow. 'Yeltsin let power slip from his own hands, and it was picked up by others, such as oligarchs, regional leaders and criminal groups.'
Mr Berezovsky befriended Yeltsin's daughter, Tatiana, and by many accounts became a regular fixture in Yeltsin's Kremlin office. In his 2000 biography, The Godfather of the Kremlin, the American-Russian journalist Paul Klebnikov - the editor of Forbes Russia, who died in a still-unsolved 2004 contract murder - detailed Mr Berezovsky's rise through Russia's crime-infested business world, Klebnikov said, by exploiting political contacts to acquire state assets at far below their book value.
But it was his alleged mastery of political intrigue that made Mr Berezovsky's dark reputation. In 1996, as a visibly ailing and deeply unpopular Yeltsin appeared likely to be trounced in presidential polls by his communist challenger, Mr Berezovsky rallied Russia's seven richest men - 'the Oligarchs' - to throw their resources behind the old leader. After a campaign marked by allegations of dirty tricks, media corruption and voter manipulation, Yeltsin won. He rewarded Mr Berezovsky with a series of government posts that critics say helped further his interests.
In 1999, as Yeltsin's grip on power faltered, it was Mr Berezovsky who claims to have promoted the unknown Vladimir Putin as the heir apparent. However, once safely ensconced in power, Mr Putin turned on his erstwhile sponsor, causing Mr Berezovsky to flee.
Many experts say that Mr Berezovsky's feats have been inflated. 'Berezovsky is a master of political theatre; he does conjuring tricks that people take for the real thing,' Mr Mukhin says. 'But he's a demon, there's no doubt about that.'
It is just possible that Mr Berezovsky is Mr Putin's 'personal demon', much as the renegade Bolshevik Leon Trotsky tormented Soviet dictator Joseph Stalin until an ice pick to the brain stopped him.
He may, or may not, still be dangerous. But there seems little doubt that Mr Berezovsky will retain his starring role in Russia's unfolding political drama for at least a while longer.