Comedy terrorist Aaron Barschak is facing a jail sentence after being convicted of vandalising artwork by Turner nominees the Chapman brothers.

District Judge Brian Loosley said: "This is a serious offence of wanton destruction of a work of art and I will be considering a custodial sentence."

The comic, who gatecrashed Prince William's 21st birthday party at Windsor Castle earlier this year, had tried to argue that he was creating a work of art when he splattered red paint over the piece at the Modern Art Oxford gallery.

But judge Loosely rejected the claim, branding 37-year-old Barsack, from Golders Green, North London, an attention-seeker and convicting him of causing criminal damage.

"I may well want to pass a custodial sentence to reflect my displeasure," he told the comic.

"I feel that this was a publicity stunt and not a genuine attempt by you to create a work of art.

"I'm not prepared to tolerate damage to works of art in Oxford or anywhere else for that matter."

In May, Barschack gatecrashed a private talk by Jake and Dinos Chapman at the gallery, which was hosting their exhibition, The Rape of Creativity, featuring cartoon heads superimposed on a series of etchings by Spanish painter Goya.

He hurled the paint at Chapman with a shout of "Viva Goya", the court heard.

Barschak did not take the stand during the one-day trial but claimed in police interviews that he was "collaborating" with Jake Chapman, making his own piece of art in the same way the Chapmans had adapted another artist's work.

The comic will learn his sentence on November 24, but was ordered to pay £300 costs.