LONDON - J.K. Rowling is to say goodbye to Harry Potter with a handwritten set of fairytales mentioned in her last wizard saga that she will auction for her children's charity.
Fans hoping for another dose of Potter will be disappointed as the tales will not be published, but Rowling said on Thursday she was half-way through writing another children's book.
A copy of The Tales of Beedle the Bard with illustrations by the author is to be sold at auction next month to raise money for The Children's Voice charity she set up.
"Writing it has been the most wonderful way to say goodbye to a world I have lived in for 17 years," said the author of the teenage wizard stories that have sold more than 350 million copies and made her the first billionaire author.
The Tales of Beedle the Bard are mentioned in the last Potter book as having been left to Harry's friend Hermione by their head teacher Albus Dumbledore, recently outed by Rowling as being gay.
Of the five wizarding fairytales only one -- The Tale of the Three Brothers -- is told in Harry Potter and the Deathly Hallows. She has produced just seven copies, bound in brown leather and decorated in silver and moonstone designs.
"Six of these books have been given to those most closely connected to the Harry Potter books during the last 17 years," Rowling said in the book's dedication.
"This seventh copy will be auctioned; the proceeds to help institutionalized children who are in desperate need of a voice. So to whoever now owns this book, thank you -- and fair fortune be yours," she added.
Auctioneers Sotheby's believe the copy being put on sale could go for up to 50,000 pounds ($136,851). The buyer will not be given any copyright and reproduction will be prohibited.
Her charity, The Children's Voice, campaigns for child's rights across Europe, particularly Eastern Europe.
"It's a huge silent scandal how many children within Europe are institutionalized -- a child with mental health issues who has been taken from their family or given by the family to an institution and then placed in a cage," Rowling said.
Reflecting on the fictional world of the teenage wizard that has dominated her life for almost two decades, Rowling said: "It's like coming up from a deep dive."
"It's been therapeutic in a way and I just want to say goodbye," she told the BBC in an interview. She then revealed: "There is a half finished book for children that I think will probably be the next thing that I ... publish."
Rowling has expressed surprise over the fuss that greeted her revelation over Dumbledore.
"Do I think a gay person can a be a moral compass? I think it's ludicrous that we are asking that question in the 21st century. The Christian fundamentalists were never my base."