A rare Harry Potter prequel handwritten by author J.K. Rowling on a postcard has been stolen during a burglary in central England, police said on Friday as they appealed for help from fans of the wizard across the world.

The 800-word story, set three years before Harry Potter is born and which sold for 25,000 pounds ($32,152) at a charity auction in 2008, was stolen from a property in Birmingham between April 13-24.

"Please don't buy this if you're offered it," Rowling wrote on Twitter. "Originally auctioned for @englishpen, the owner supported writers' freedoms by bidding for it."

The proceeds of the auction were donated to English PEN, an organisation which champions freedom of expression, and to Dyslexia Action.

"The only people who will buy this unique piece are true Harry Potter fans. We are appealing to anyone who sees, or is offered this item for sale, to contact police," said Constable Paul Jauncey from West Midlands Police.

Handwritten over two sides of an A5 postcard, the untitled prequel features the characters Sirius Black and Harrytarget="_blank"'>