Russian President Vladimir Putin faces the toughest test of his rebranded leadership as he grapples with fearless feminist punk and rock stars and their friends worldwide as the Pussy Riot trial goes under way.

Putin found an unexpected ally in Conservative British Prime Minister David Cameron during a visit to the London Olympics when he was shielded from tough questioning in a Kremlinesque news management In the British capital.

Journalists were discouraged from asking Putin questions on key issues that have frosted British-Russian ties, including the 2006 murder in London of Russian dissident Alexander Litvinenko, poisoned with a radioactive isotope.

Human rights issues and polarization of Western and Russian and Chinese positions on Syria and Iran also received short shrift as Cameron concentrated on capitalizing on Vladimir's presence to boost British trade.

It was Putin's first visit to London in seven years -- a period marked by his transformation from president to prime minister and then president again, a prolonged chill over the Litvinenko killing and other disputes on foreign policy, human rights, bilateral business and trade.

Russia has refused British requests for the extradition of the chief suspect in the Litvinenko case, former Soviet KGB agent Andrei Lugovoi, who denies involvement.

British acquiescence led to Putin dominating the headlines with a statement in which he said he hoped the court trying the Pussy Riot trio would be lenient.

Critics and media analysts said orders for the girls' prosecution appeared to have come right from the top.

Rather than focus on the group's song that mocked Putin, the president criticized the band's appearance in Moscow's Christ the Savior cathedral in February.

During that appearance, the punk group performed an anti-Putin "punk prayer" to highlight the Orthodox Church's support for the powerful president.

"There is nothing good in this," Putin said. "I wouldn't really like to comment but I think if the girls were, let's say, in Israel, and insulted something in Israel ... it wouldn't be so easy for them to leave." If they "desecrated some Muslim holy site, we wouldn't even have had time to detain them," he added.

"Nonetheless, I don't think they should be judged too severely for this," Putin said. "But the final decision rests with the courts -- I hope the court will deliver a correct, well-founded ruling."

Critics said the London news conference gave Putin an opportunity to maneuver in response to global outrage over the trial of Pussy Riot activists Maria Alyokhina, Nadezhda Tolokonnikova and Yekaterina Samutsevich. The feminist collective members face up to seven years in prison if found guilty on charges of hooliganism motivated by religious hatred.

Defense lawyers have called the case a show trial with its absurd dimensions growing at each court session.

Leading musicians in a letter to The Times newspaper denounced "preposterous" charges against the band.

"We believe firmly that it is the role of the artist to make legitimate political protest," Jarvis Cocker, Pete Townshend and Neil Tennant wrote. "As he visits the United Kingdom this week, we ask President Putin to ensure these three women receive a fair hearing."

Litvinenko's widow, Marina, said she was dismayed by Putin's visit and asked Londoners to wear "a white ribbon, the symbol of Russian protest."

Carole Cadwalladr wrote in The Observer the Pussy Riot protest "seems certain to become a defining moment in Putin's political career.

"It is, many people say (practically everybody, in fact), a moment when Russia's future is, in some as yet undetermined way, being decided," Cadwalladr wrote.