J.K. Rowling has urged fans not to buy the stolen prequel to the 'Harry Potter' franchise she donated to charity.

J.K. Rowling

J.K. Rowling

The author of the world renowned novels - which were tuned into a blockbuster movie franchise by Warner Bros. Pictures - has been left dismayed by the news that the 800-word story she wrote down on both sides of an A5 postcard to raise money for a good cause was stolen from the owner's Birmingham home last month.

Rowling posted a message to her 10 million fans on Twitter saying: "PLEASE DON'T BUY THIS IF YOU'RE OFFERED IT. Originally auctioned for @englishpen, the owner supported writers' freedoms by bidding for it. (sic)"

The work was auctioned off nine years ago and sold for £25,000.

Set three years before Harry Potter was born, the short story focuses on the boy wizard's father James Potter and his godfather Sirius Black when they were teenagers.

Following a confrontation with two "muggle" policeman after a motorbike chase, the magical pair manage to escape on broomsticks.

West Midlands police are appealing to Potter fans to look out for the item and if they have any information to contact the force immediately.

Investigating Officer PC Paul Jauncey said: "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."