If there's one thing that's never been lost on Vladimir Putin, it's the power of visual imagery.

Remember all those carefully posed shots of the Russian president, stripped to the waist as he swam and fly-fished in a Siberian river, rode bareback and tended a campfire? Was that the same trope of macho virility that we saw wrestling with a big brown bear? No, I must have imagined that one. Not that he couldn't, you understand.

Well, the three-times Russian leader has met his match. When David Cameron shakes hands with Vlad the Lad in London today, I hope our PM will make it clear which side he's on in what's being called "Putin v the Punks".

The punks are three pale, thin young women stuck behind the bars of the glassed-in dock of a Moscow courtroom. It's the sort of arrangement created for mass murderers. Yet their "crime" was to stage an impromptu performance of a hymn with an anti-Putin lyric in a historic Russian Orthodox church in February. The offending line was something like: "Please Virgin Mary, get rid of Putin".

Everything about this energising piece of performance art, which wouldn't have been out of place at the opening ceremony of the Olympics, was carefully choreographed. The three women are members of a 10-strong leftist, feminist punk-style group, who go by the witty moniker Pussy Riot. But they don't look like rioters. Instead, they adopt gaudy clothes in primary colours and bright balaclavas, not merely to conceal their identities but to carry the message that they speak for all Russian women in a country that has sidelined female emancipation.

The location of the protest was deliberate too: Moscow's Cathedral of Christ the Saviour. It was to draw attention to the unhealthily symbiotic relationship that has developed between the Russian Orthodox Church and the Putin regime. Under the state-sponsored atheism of the Soviet era, priests risked imprisonment, torture and execution to keep the Christian faith alive. Since the fall of communism, the church has become strongly aligned with Russian nationalism and the increasingly repressive Putin-Medvedev administration.

The protest song took less than a minute. It was mimed, with the cheeky lyric dubbed in later, and would have sunk without trace if the authorities had not responded by arresting the women and charging them with "hooliganism motivated by religious hatred". They now face up to seven years in jail and in the five months since their arrest have been denied access to their families. (Two of them have small children.)

Amnesty International, which has adopted them as prisoners of conscience, says the case is riddled with irregularities: a blatant disregard of due process, imprisonment without trial, the refusal of bail and lack of time to prepare their case, in a country where few believe the judiciary to be independent. (Just 1% of Russian trials result in not guilty verdicts.)

There's no doubt that Pussy Riot's protest was offensive to Orthodox Christians but in a democracy such dissent is legitimate and the administration's hyper-reaction has shocked even Putin supporters, some of whom have signed an open letter condemning the trial. If the Pussy Riot protesters are sent down for years, just watch the 1.5m who have watched their performance on YouTube swell tenfold.

That is what could make this a defining moment. Putin may be safe for now but this ridiculous over-reaction is evidence of an increasingly repressive attitude towards dissent. He once represented stability and rising living standards. Now growth is stalling, along with falling gas and oil prices and the old welfare state is crumbling. The arrest on Tuesday of anti-corruption blogger Alexei Navalny on apparently trumped-up charges is another straw in the wind. A lumbering Russian bear that hates to be mocked is ultimately no match for a nimble protest movement, which, like Occupy, uses the internet and flash protests. My roubles are on the gels in balaclavas.