Flashpoint: Bianca Jagger and theatre critic's spat at the opera

It was one of the arts events of the year: audiences in Britain had waited nearly four decades to see a complete performance of Philip Glass's five-hour, abstract opera Einstein on the Beach, which was devised in 1976 with the avant garde American director Robert Wilson.

Rage was not scheduled to be the keynote of this long-anticipated event. But an unlikely and bitter feud has broken out between theatre critic Mark Shenton and environmental campaigner Bianca Jagger, whom Shenton has accused of repeatedly taking flash photographs at the event. Jagger has denied that she did so, and accused Shenton of assault – a charge he in turn denies.

According to Shenton, who wrote a detailed blog about the incident for the Stage, he became aware of flash photography being used during the performance by a member of the audience, and eventually noted that the culprit was a woman sitting about 10 seats away from him in row D of the Barbican theatre stalls.

At the end of the performance he asked an usher to summon the house manager to remonstrate with the person who had breached this most basic of theatre etiquette rules.

When no one appeared, and as the standing ovation faded, he approached the woman himself – in "full Patti LuPone mode", as he wrote. At this point, he had no idea of her identity but, he told the Guardian, "I said, 'Who do you think you are and what the hell do you think you were doing?'" The woman, he said, brushed him off. A few moments later a fellow audience member informed Shenton that the woman was Jagger.

In the comments section of Shenton's blog, Jagger herself waded in, accusing Shenton of "physical assault and abusive behaviour ... His behaviour is objectionable and I am surprised by all those who without knowing the facts will justified [sic] such abusive behaviour. I thought that violence is [sic] always condemned."

Shenton denies the accusation of assault: "I did not lay a finger on her," he told the Guardian.

She continued: "I snapped a couple of photographs during [the] curtain call, many others were taking photographs during the performance ... Mark Shenton pushed everyone in the row where I was sitting, before assaulting me."

Shenton said: "There are clearly no rules any more. This is clearly civil breakdown in the theatre."