A pencil drawing by Bradford-born artist David Hockney has rocketed beyond its estimate at auction.

The picture – an iconic image of the counter culture 40 years ago – called ‘Naked Richard Neville’ went under the hammer at Bonhams in London today for £27,600.

Experts had expected the full-frontal nude drawing of Neville, who was editor at Oz magazine in 1970, to fetch £10,000 to £15,000.

It was for sale as part of Bonham’s Post War and Contemporary Art and Design sale.

It was drawn by Hockney, now living in Bridlington, in 1971 to raise funds for the infamous Oz obscenity trial.

The former Bradford Grammar School pupil and graduate of Bradford Art College and the Royal College was one of dozens of artists who donated works to the defence fund. The scandal focussed on a Rupert Bear parody published in the magazine in 1970 and edited by teenagers. The original drawing of Neville and his fellow editors, Felix Dennis and Jim Anderson, who also posed nude, were put up for auction at the time, along with numbered lithographs, combined into a triptych.

The trial became a cause celebre testing boundaries on censorship which had remained largely unchallenged since the Lady Chatterley’s Lover court case in the early 1960s.

The three were found guilty and sent to prison where the shaving of their heads caused more controversy, though the convictions were later overturned.