The work, inspired by Andy Warhol's iconic portrait of Marilyn Monroe, was one of 75 pieces of 'urban art' on sale, Bonhams auction house said.

Many of the works were created with spray-paint and stencils and began life as street graffiti before being transferred to canvas.

'By definition (urban art) is an ephemeral art form, often disappearing as fast as it appears,' Mr Gareth Williams, senior picture specialist at Bonhams. '

By transposing their images from street wall to canvas, urban artists are now creating a permanent legacy.'

Banksy refuses to give his real name, which has been variously reported as Robert Banks or Robin Banks. The artist, who does much of his work on exterior walls, rarely offers originals for sale. -- AP