If Vladimir Putin is the enigmatic Mr Hyde of 21st-century Russia, then Mikhail Khodorkovsky is its Dr Jekyll. He’s an oligarch, a plutocrat, a political player and a contemporary of Putin who nonetheless seems to be the good guy. He appears entirely sincere in his commitment to democratic reforms in Russia and seems to float free of the glowering gangster code of omertà that governs all those who enriched themselves at Putin’s tsarist court. Khodorkovsky first became wealthy as the proprietor of Russia’s first private bank in the Yeltsin 90s. Then he participated in the country’s privatisation scam, whereby impoverished Russian citizens were forced to sell their valuable share certificates to Khodorkovsky and his ilk for a song; Khodorkovsky and others finally loaned money to the near-bankrupt state in return for the right to buy up national utilities later at bargain-basement prices.

Alex Gibney’s absorbing new film shows his remarkable metamorphosis throughout this. While all the other post-Soviet wiseguys just bulked up and looked ever more morose and fractious (there is a startling glimpse of Roman Abramovich who has this characteristic oligarch sulk-frown) Khodorkovsky became smilingly sleek and telegenic as he voiced his political concerns. With close-cropped hair, rimless spectacles and a black sweater tucked into his blue jeans, he looked like a combination of Steve Jobs and Jerry Seinfeld.

Meanwhile, Putin’s face seems ever more puffy and waxy, perhaps the result of having had cosmetic work done. In his London exile, where he sponsors anti-Putin activism, Khodorkovsky seems untroubled by the fact that so many Putin critics have met violent ends in the UK. It may still happen to him – something this new documentary does not directly address. Khodorkovsky is shown getting London tubes and trains on his own, like a British commuter, with no obvious security guards. But surely he must travel with at least two or three burly guys.

Facebook Twitter Pinterest Mikhail Khodorkovsky served 10 years in prison. Photograph: Courtesy: TIFF

His easygoing calm has something to do with having been put in prison in 2003 – after challenging Putin on the corruption issue – on trumped-up charges of tax evasion and embezzlement. As the film about him acidly points out, these accusations could hardly be more meaningless: the wealth and prestige of the mega-Croesus class that governs Russia is founded on wholesale larceny of state assets. Khodorkovsky repeatedly threatened hunger strike in prison and was ready to face death. After 10 years, Putin freed him. Whether Putin likes it or not (and of course he doesn’t), Khodorkovsky’s talent for communication, his flair for television and political rhetoric and the very fact of having served a prison sentence widely seen as unjust makes him look like a Dostoevsky or a Solzhenitsyn for our time.

But the fact remains that Khodorkovsky is a Putin-vintage oligarch and he didn’t get that rich by being a nice guy. The Putin government has repeatedly tried to suggest that Khodorkovsky was involved in the 1998 murder of Vladimir Petukhov, the mayor of Nefteyugansk, the remote Siberian town where Khodorkovsky had enraged Petukhov by laying off thousands of local workers employed by his oil company, Yukos. Gibney takes it as read that it had nothing to do with Khodorkovsky, and indeed nothing was proved.

The last film about him, Cyril Tuschi’s Khodorkovsky, was a semi-dramatised documentary that was made in 2011 when he was still in prison and it conferred on its subject more of a tragic mystique than Gibney’s film. This one interviews Khodorkovsky in his London exile as if things are basically settled, at least as far as he is personally concerned. Perhaps that is true and perhaps not. I felt that Gibney had not exactly solved the sphinx riddle of Khodorkovsky’s seraphic calm; he does not question him closely about his personal life.

But his film does present Khodorkovsky in context in a way that I haven’t seen before. He was the oligarch smart enough – and ruthless enough – to do as well or better than anyone in the Yeltsin/Putin free-for-all years, and then his smartness and ruthlessness perhaps gave him a perspective on it all. I think he simply became bored with mega-riches and, instead of buying a football team or buying power, what Khodorkovsky bought was criticism-of-power, a position of prominent dissidence normally afforded to writers and artists, and which Khodorkovsky achieved semi-accidentally through imprisonment, which he met with stoicism. What a strange story – and it’s not over yet.