Russia's former world chess champion Garry Kasparov has given up the game he dominated for 20 years in order to take on a new opponent - Vladimir Putin. The BBC's Moscow correspondent Rupert Wingfield-Hayes watched him at work.
Mr Kasparov is a phenomenon. In 1985 he became the world's youngest ever chess champion at the age of 22.
Mr Kasparov's personal style is very different to Russia's political elite
He went on to dominate the chess world, beating all comers, and remaining the world's number one chess player for 20 years.
Mr Kasparov, in other words, is not to be underestimated.
But in his newly-chosen calling he faces very different opponents, who rarely play by the rules.
I met Mr Kasparov standing at a bus stop outside St Petersburg airport.
Sporting a denim jacket and blue baseball cap he looked nothing like the average Russian politician.
They usually wear shiny suits and hide behind the dark tinted windows of large German limousines.
The one thing Mr Kasparov does have these days is bodyguards, large men with thick necks and dark glasses. Russian politics is a dirty game.
Mr Kasparov was on his way to lead a political rally in Russia's second city.
He is trying to unify the disparate groups that make up Russia's fractured and marginalised political opposition.
Since Vladimir Putin came to power here seven years ago, political opposition to the Kremlin has all but disappeared.
The Russian parliament is dominated by two pro-Kremlin parties, United Russia and A Just Russia.
Much of the mainstream media has come back under Kremlin control and the voices of dissent have been gradually silenced.
Garry Kasparov was arrested during a rally in April
Mr Kasparov believes real political opposition to Mr Putin can now come only from outside parliament, and that means taking to the streets.
In St Petersburg the weather was good, and the diminutive grey-haired chess player was in a feisty mood.
"Any police state is nervous about street protests," he says.
"They know that lots of people are unhappy. Today it could be 5,000, tomorrow 50,000. The regime feels it is unstable. It feels the growing protest."
A crowd began to gather by mid-afternoon in the heart of St Petersburg. But it was not like any political protest I have ever been on before.
Anyone wanting to join the march first had to show their identity papers to the police, and pass through a metal detector and body search.
An hour later, the crowd had swollen to 1,000 people but they were still far outnumbered by the ranks of police.
On a march in Moscow two months earlier thousands of police in full riot gear had stormed in to the crowd, cracking heads and dragging away protesters.
For the Kremlin it was a public relations disaster, and they seem to have learned a lesson.
With Mr Kasparov in the lead the march headed off.
Liberals and environmentalists marched side-by-side with right wing xenophobes - a very odd collection.
The march ended with a whimper, a half-hearted rally on a patch of grass in front of an old church.
The 'New Russians'
A crowd of onlookers gathered in the park across the street, making sarcastic remarks.
"Who are these losers?" one man commented, "what are they complaining about?"
After the march, I headed across town to meet a young Russian family at St Petersburg's massive new Ikea store.
Jenya, 24, and her husband are what are generally referred to here as "New Russians" - people who have benefited from Mr Putin's rule.
Jenya and her husband both speak English. She is studying for a PhD in law and her husband is an engineer at the new Toyota car plant.
They are liberal, western-looking. But they simply cannot understand why anybody would take to the streets to oppose Mr Putin.
Little to fear
"I don't understand these protest activities," she told me. "I'm not saying Putin is the best, but would the alternative be better?"
"Our lives are getting better every year. I hope they will continue to get better. I wish Putin could stay on for another term," she said.
And that is the simple truth. Mr Putin may be increasingly disliked outside Russia.
But at home he enjoys popularity ratings US President George W Bush and British Prime Minister Tony Blair only dream about.
Yes, he has stifled public debate; yes, he has rolled back democracy; yes, his secret police are once again the most powerful organ of the Russian state.
But, for most Russians, Mr Putin is a saviour, the man who brought them stability and prosperity after the dark days of the 1990s.
Mr Putin has been lucky. Without sky-high oil prices it might be a very different story. But, for now, the former secret policeman seems to have little to fear from the former chess champion.