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

The 800-word story, set three years before Harry Potter is born and which sold for 25,000 pounds ($A43,500) at a charity auction in 2008, was stolen from a property in Birmingham in mid-April.

“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.

Author J.K. Rowling urges fans to be on the look-out for the stolen manuscript.

“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 Harry’s father James.

It opens with a youthful Sirius and James cornered by two irate policemen at the end of a high-speed motorcycle chase.

After an exchange of words with the policemen, the two teenagers make their escape using a touch of magic.

The card concludes with the words “From the prequel I am not working on — but that was fun!”

More than 450 million copies of the seven original Harry Potter books have been sold worldwide in 79 languages. The movie franchise has grossed more than $US7 billion worldwide.
-AAP