LONDON (Reuters) - The secret of what happened before boy wizard Harry Potter went to Hogwarts will be revealed through the unusual channel of a charity auction next month.

Author JK Rowling has penned an 800-word outline of a prequel to the seven book series that has made her into a billionaire which will be sold at the auction on June 10 by bookseller Waterstones.

The outline, which ends with the line "From the prequel I am not working on -- but that was fun!" is one of 13 story outlines written for the auction by famed authors including new Bond writer Sebastian Faulks and Nobel laureate Doris Lessing.

"What's Your Story? just gets more and more exciting -- all these brilliant works by amazing writers and illustrators, every one a small masterpiece," said Waterstone's chief Gerry Johnson.

"We never dreamed that JK Rowling would donate something so precious, and we're incredibly grateful."

The money raised will go to charities English PEN and Dyslexia Action.

Other authors who have donated outline works are Lisa Appignanesi, Margaret Atwood, Lauren Child, Richard Ford, Neil Gaiman, Nick Hornby, Michael Rosen, Axel Scheffler, Tom Stoppard and Irvine Welsh.

Source: Reuters