Occasionally I get asked who is the most charismatic person I’ve interviewed, and, for the past 14 years, I’ve given the same answer: Garry Kasparov. A chess player? People reply. Absolutely, I say. Chess, like boxing, that other great blood sport, like, indeed, Russian politics, is about directly destroying your opponent; Kasparov did that over 64 squares more effectively than anybody else. Up close, you could see why. Intellectually, physically, the man known as the Beast of Baku gave new life to the cliché animal magnetism.

Having met him again, I see no reason to demote him. He retired from professional chess, no longer world champion, but still ranked number one, in 2005. He is now a writer, politician and ardent opponent of Russian president Vladimir Putin. We met in Stockholm, where Kasparov was about to give a talk based on his new book, How Life Imitates Chess, to 250 businesspeople. “We’ve met before,” he said, “in 1993. In Moscow.” I can’t deny I was impressed.

His book is more interesting than it sounds, though its title is rather undermined by the author’s admission that “an aptitude for chess demonstrates nothing more than an aptitude for chess”. Indeed, coming on 44 as opposed to coming on 30, Garry Kasparov has added, if not quite humility, then a measure of charm to his other qualities. Back then, his conversational style was combative in the extreme. He brooked no disagreement. I remember falling out, for instance, over the precise dates of the Spanish Inquisition.

I hadn’t been surprised when I had read over the years of his two divorces, his custody row with his first wife over their daughter, his recriminations against IBM following his defeat by its Deep Blue computer in 1997. His enormous self-belief, necessary no doubt to become world champion at 22 and to stay at the top for 20 years, tipped into arrogance. And, even allowing for the simplifications of speaking a language not his own, he’d been macho, a little flashy, keen, in the way of many of his newly enriched countrymen, to demonstrate that he’d made it on Western terms.

But Garry Kasparov has grown up. During our day together in Sweden, his company was as pleasant as the early spring sunshine. His surly niets had turned into emphatic das, he sought to build a conversation rather than deliver a monologue, he laughed a lot, and not just at his own jokes, although one of them, about local giants Ikea, wasn’t bad. “How are Ikea able to compete so well with Asia? They’ve outsourced their labour to the customer.” Maybe you had to be there: the Swedes, at least, had a chuckle.

The reason for his good humour is obvious: he isn’t playing chess any more. Not serious chess, anyway, the sort that saps energy, manners, perspective. “I play for fun on the net,” he admits. Doesn’t he win really easily? “You can find strong players.” Do they know it’s you? “They can guess, probably.” Does he miss the competition? “I have much larger competition now. I will not go back.”

Kasparov’s speech lasted an hour. The strategy/tactics, calculation/evaluation, trust-your-instincts decision-making spiel wasn’t bad, as these things go. His erudition is considerable, his argument peppered with human interest, from Mozart to Edison, Tolstoy to Verdi, Galileo to Adam Smith, with Count Bernadotte and Alfred Nobel, or Nobble in Kasparov’s accent, thrown in for local colour. He regards it as a challenge never to give the same talk twice, weaving in the facts that on this day, March 14, Albert Einstein was born in 1879, Karl Marx died in 1883 and the Treaty of Ulm was signed in 1647.

He might also have added, but possibly prefers to forget, that on March 14 in 2004, Vladimir Putin was re-elected for a second term with almost 80 per cent of the vote. Putin continues to enjoy 80 per cent approval ratings. Kasparov shrugged when I put this to him. “If a pollster calls someone in Russia and asks them about Putin, they should not expect a true answer.”

Putin’s reputation has, of course, like Chelsea FC and property prices in Kensington, benefited hugely from high energy prices. “But,” says Kasparov, “I travel from Vladivostock to Kaliningrad, Murmansk to Krasnodar and people ask, ‘Why is the country getting richer and we are getting poorer?’” As for the 2004 poll, “Every election since Yeltsin’s in 1996 has been rigged.”

Kasparov was known as an ultra-aggressive player, and his political style owes much to his approach to chess. He repeatedly denounces “Putin’s corrupt regime” from the rostrum in Stockholm, calling it “disastrous” and his country “devastated”. He hasn’t met the president, he says. “I’ve met enough KGB lieutenant-colonels, one more, one less, it won’t make any difference.” He is a leading player in a new anti-government coalition called Other Russia, which earlier this month held a rally in St Petersburg, violently broken up by the police, but not before Kasparov and others had addressed the crowd. Other Russia’s manifesto, he says, is, “Free and fair elections, no censorship, decentralisation, the dismantling of the current regime.” More rallies are scheduled to take place in a fortnight.

Kasparov’s own pressure group, United Civil Front, has published investigations into the Beslan school carnage and the Nord-Ost theatre siege, which ended with hundreds debilitated by a mystery government-produced gas. He has established a fund for the victims of terrorism.

Inevitably, before long, our conversation turned to Alexander Litvinenko, the KGB-officer-turned-Putin-critic who was poisoned in London last autumn. “When I heard about polonium I had no doubts,” says Kasparov. “I know the address where you can find the true killers, it’s the Kremlin. But there are many groups there. I don’t think it was Putin who ordered it. I don’t think so. But I believe that those who ordered it, they see Putin probably every day, it’s his inner circle. Each head of a KGB department can run his own operation because they’re so rich and so powerful. I don’t want to waste my intellectual power trying to unveil these spy games.”