Collector and businessman Nick Yates paid “a few hundred pounds” for a framed work because the sketch it contained seemed “vaguely familiar”.
But it was only when he took it to be reframed that the drawing was identified as a preparatory sketch for one of the Bradford artist’s most famous pop art paintings. A Bigger Splash was produced by Hockney during his stay in California in 1967, and hangs in the Tate Modern.
Yorkshire gallery owner Steven Lord, who identified the sketch, said the composition was “almost identical” to the finished painting.
He said: “On the reverse are further sketches, which is typical of an artist who is playing around with ideas in a sketchbook prior to committing paint to canvas.
“It is signed with Hockney’s rather unusual signature with a greeting so we can assume that he gave it away as a little memento.”
Mr Lord said Hockney’s fascination with “super bright lights of California, after the dullness of Bradford” led him to create the acrylic painting.
The sketch will go on public display in West Yorkshire next week at the Harrison Lord Gallery, as part of the Brighouse Festival, prior to being sent to London for a valuation.