As the critics were keen to point out last year, Damien Hirst's primary expertise does not lie in drawing or painting.

Even if it did, Hirst would be the first to admit that the sketch owned by GCSE student LJ was not his finest work. Nevertheless, to LJ's giggling delight, bidders proved very competitive over it at Dreweatts and Bloomsbury's Urban Art sale on Wednesday (April 21).

The sketch, a straightforward combination of three scrawled Hirst themes: a shark, sparkling skull and butterfly on ordinary lined paper, is completed with "For LJ Don't give up on the Art!!!" with a heart sign and a trailed signature - probably the most valuable part of the piece.

LJ didn't meet Hirst himself, but his father is a cab driver, and when he took Hirst from his houseboat to Clariges for a meeting he mentioned that his son had an Art GCSE looming and asked for his autograph. The artist needed no persuading to produce the cheerful doodle and message.

Ahead of the London auction the work was given an estimate of £1,000-1,500. But whether due to curiosity or as an investment, frenetic bidding quickly pushed the piece to 10 times that, and it was taken away by a happy bidder for £14,640.

LJ will be spending the proceeds on professional camera equipment as he wants to be a film director and is giving his mother £200 to spend in Oxford Street with her best friend.

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