A popular genre of art hoax involves a collector being conned into praising (and often buying) a work of art that he believes to have been done by a great artist, but which is later revealed to be the work of an animal or a young child. (See Monkey Art Fools Expert
.) An example of this hoax is reported by Keith Allen in his autobiography, Grow Up
. The Telegraph reports
The esteemed theatre director Sir Trevor Nunn was left with a face the colour of a blank canvas after being told the £27,000 painting he had splashed out on really was thrown together by a two-year-old and his friend. Sir Trevor had spent the money on a work by Damien Hirst - only to be told during a later conversation with the artist that it was created by two children. In fact, Hirst claimed that the piece, one of his "spin paintings", was a collaboration between his son Connor, who was two at the time, and the actor Keith Allen's son Alfie, younger brother of the pop singer Lily Allen, who was 10.
There's no verification that this actually happened, so perhaps Allen was simply making up an amusing story. However, the Telegraph notes that Sir Trevor later sold the same painting for £45,000. (Thanks, Joe)