Student William Hackman gambled £35 on a postcard - and discovered it was a work of art worth £4,000.
William picked out the card in an exhibition at London's Royal College of Art and took a chance it would be worth his investment.
Only after stumping up his cash did he learn the sketch was by controversial artist Damien Hirst.
However, William, 22, admitted he didn't like the picture or rate the artist.
William, who is studying French and business at Brighton University, said: "On a scale of one to ten, I'd give it one.
"I much prefer the work of people like Roger Cecil and Terry Frost. Hirst is obviously intelligent and talented but I think he could try harder."
The sketch of the phrase I Love You shows an eye, a heart with arteries and the letter U.
The postcard was one of 2,000 in the fund-raising exhibition but only a handful were worth anything.
The artists' identities were kept secret until buyers parted with their money.
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