An 800-word Harry Potter 'prequel' by J.K. Rowling, set three years before the boy wizard is born, has been sold for £25,000 at a charity auction.

Thirteen authors contributed to the sale, in aid of English PEN and Dyslexia Action. Works by Sir Tom Stoppard and Doris Lessing raised £4,000 and £3,000 respectively.

The story, written last month, is not intended to become a book, Rowling says. At the end of the tale, written on both sides of an A5 storycard, the millionaire author writes: “From the prequel I am not working on - but that was fun!”

Organisers of the charity auction asked 13 authors, including Rowling, Margaret Atwood, Sebastian Faulks, Nick Hornby and Doris Lessing, to create a story for the sale.

The writers were told they could submit anything from a doodle and collage to a fresh story.

Rowling, who has earned a £560 million fortune from the seven Potter stories which sold more than 375 million books worldwide, sets her story three years before Harry is born and features the characters Sirius Black and James Potter, Harry’s father. They get in a scrape with irate policemen before making their escape via broomsticks, drumsticks and a little bit of magic.

“I had great fun writing the card and I’m absolutely delighted that it has raised £25,000 for two such worthy causes,” Rowling said.

The author, whose books have also been turned into a series of record-breaking films, has previously stated that if she did write another Potter tale, it would not be for another ten years.

A Waterstone's spokesman revealed to Times Online that the buyer of the Potter prequel is Hira Digpal, the president of Red-33, a Tokyo-based investment-banking consulting company. Other high bids from last night’s auction included Tom Stoppard’s card, which sold for £4,000 and Doris Lessing’s which raised £3,000.

Money raised from the sale at Waterstone’s in Piccadilly, Central London, will go to English PEN, which promotes understanding through literature, and Dyslexia Action.

In December last year, a new JK Rowling work, The Tales Of Beedle The Bard, fetched £1.95 million at auction.

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