Banksy had bailed two members of the Russian arts collective Voina ("War") out of a horrific St Petersburg prison, where they were being held indefinitely awaiting trial. Voina is known for many provocative pieces, including the giant penis painted on a drawbridge facing secret police headquarters. Leonid Nikolayev and Oleg Vorotnikov and Oleg's wife have since been cruelly beaten by secret policemen who also brutalized Oleg's toddler, Casper. The pair now face punitive psychotherapy, a practice widely feared in the Soviet era, when dissidents were committed to ghastly asylums.

Oleg and Lenya emerged triumphant and boasted that they had recruited some more Voina members inside the pre-trial jail. But the charges against them still stand.

In fact, there is a risk that they may be re-incarcerated and subjected to psychiatric tests, which lawyers say the investigator in charge of the case has asked for.

"This looks like the return of punitive psychiatry," said Igor Ryabchikov, Oleg's lawyer, referring to the Soviet-era tactic of forcibly sectioning dissidents.

The lawyer also intends to fight his client's tough bail terms – which include an obligation to give the authorities two hours' notice every time he wants to leave the house. If he is ever deemed to have broken the conditions, he will be rearrested and Banksy's money will be forfeited.

Ironically, Voina's penis-on-the-bridge stunt titled A Dick Captured by the FSB was recently nominated for a state prize for contemporary art – only to be mysteriously removed from the shortlist a week ago.