JK Rowling has written a short prequel to her popular Harry Potter books.

She is one of 13 authors - including Nick Hornby and Doris Lessing - asked to write storycards by Waterstone's for their What's Your Story? auction.

But the 800-word tale will not be published - instead it will go under the hammer at a charity auction in London next month.

Rowling's story finishes with the handwritten words: "From the prequel I am not working on - but that was fun!"

Source: Press Release