One day in 1990, a bullnecked ex-con stepped out of Russia’s prison colony AN-24/34, wearing a dated Soviet suit that showed he’d been locked up for quite some time. Yevgeny Viktorovich Prigozhin, a street hood and mugger, had just done 13 years for robbery, and had little going for him except a prison-issue train-ticket home to St Petersburg.

With the old Soviet Union already collapsing, the prospects for such an ex-jailbird looked thin. Yet during Russia’s drift into lawlessness in the 1990s, the very traits that had landed Prigozhin behind bars would stand him in good stead as a businessman, paving his rise from hot-dog vendor to mercenary-group boss.

“Ambition, enterprise, cunning and a willingness to use violence and threats would be essential to prospering in this world, and Prigozhin had them all,” write Mark Galeotti and Anna Arutunyan in Downfall, their new biography of Prigozhin. It’s aptly named: their subject died last August in a mysteriously well-timed plane crash, two months after sending his mercenaries, the Wagner Group, to march on Moscow.

As the authors drily note in their foreword, Prigozhin’s death came just a month after they’d signed the book contract, sparing them a ponderous “only-time-will-tell” ending. Ebury, their publisher, may also have felt relieved: Prigozhin routinely issued lawsuits and death threats to journalists. One Moscow hack inquired about doing a “vanilla” day-in-the-life piece on Prigozhin’s eldest daughter; the journalist was warned that she would be car-jacked and raped.

Downfall is a psychological profile of a man who, even more than Putin himself, personified the ruthless gangster-capitalist class that rules Russia today. Born into a middle-class Russian family in 1961, Prigozhin initially hoped to become an elite Soviet skiier; but he fell in with a street gang as a teenager. While the book suggests he got “mixed up with the wrong crowd”, he quickly adjusted to underworld life. When he was sent to prison in 1981, he had, the authors say, a domineering “inner cruelty” that stopped even hardened criminals intimidating him.

On return to freedom in St Petersburg, he sold hot-dogs, which was a far more significant gig than it sounds. Fast food, like Coca-Cola and denim jeans, was hugely profitable in the immediate aftermath of the Soviet Union’s collapse. Prigozhin’s success as a Russian Colonel Saunders lay not in the secrets of his mustard – mixed in his kitchen – but in stopping other criminals muscling in on his pitches. “Making money may have been easy,” the authors observe. “Keeping it (and your life) was not.”

He then expanded into fine dining, opening two of St Petersburg’s best restaurants, where gangsters, oligarchs and politicians would mingle – including one Vladimir Putin, then a rising City Hall apparatchik. Cannily, Prigozhin would make a point of personally serving food to his VIP guests, who also included visiting dignitaries such as George W Bush and Tony Blair. The genial waiter was less nice to his own staff. After a customer complained about their tomatoes, one employee was hospitalised for two months.

Through playing maître d’ to the elite, Prigozhin won lucrative government catering contracts, earning his nickname of “Putin’s chef”. His crowning success, though, was as an “adhocrat”, delivering whatever shadowy services the Kremlin couldn’t be seen doing itself. Hence the “troll farms” that flooded the internet with pro-Trump propaganda ahead of the 2016 US election, and then Wagner, whose mercenaries became a deniable strong-arm of Russian foreign policy in broken states such as Syria and the Central African Republic – then, fatefully, in Ukraine.

As an ex-jailbird himself, Prigozhin was a popular commander-in-chief among the convicts brought in to boost Wagner’s ranks. Soon, though, the war’s horrendous casualty rates saw him issuing extraordinary video rants against the inept “b——s” in Russian high command. At first, he claimed his problem was only with stuffed shirts such as defence minister Sergei Shoigu, who is said to have described Wagner’s boss and troops as “gopniks” (effectively “chavs”). But eventually, Prigozhin also referred with contempt to a certain “happy grandpa” in the Kremlin. The government hit back by ordering Wagner’s forces to sign official contracts, effectively disbanding it – whereupon Prigozhin decided he’d had enough.

While diligently recreating the abortive June 24 coup, Downfall makes no claim to offer any insider details, beyond saying that Prigozhin’s subsequent plane crash was “almost certainly” a Kremlin hit-job. What it does instead is delve into Prigozhin’s motives: “Watching his men die in droves, he was clearly thinking about a wider future for the country… and was horrified that he couldn’t see one.”

Many may struggle see common ground between Prigozhin and the dissident Alexei Navalny, who perished three months ago in a remote penal colony. Galeotti and Arutunyan argue, however, that both men had a “desire to see greater fairness come to Russia” – a desire that toppled first the tsars, then the Communists, and now threatens Putin too. That even a monster such as Prigozhin can be seen as a dissident shows how severe Russia’s own “downfall” has already been.

Downfall is published by Ebury at £18.99. To order your copy for £16.99, call 0808 196 6794 or visit Telegraph Books