Harry Potter's J.K. Rowling has helped to raise $3.9 million for charity after a rare copy of her latest book sold at a London auction for 40 times its estimated price.The Tales of Beedle The Bard - first mentioned in Harry Potter And The Deathly Hallows, is a hand written and illustrated book of tales relating to the boy wizard’s final adventures. Only seven copies of the book are in existence and six of them were handed out by Rowling as gifts to those "most closely connected" to the Potter series since its conception, while one was put up for auction on Thursday to help raise money for her Children’s Voice charity.The rare book, the only one bound in brown morocco leather and mounted with silver and semi-precious stones - was sold to an anonymous bidder after going under the hammer at Sotheby’s auction house. It was originally valued at between $60,000 to $100,000. Speaking after the sale, Rowling said: "I’m stunned and ecstatic. Christmas has come early for me." Rowling founded Children’s Voice in 2005 with the aim of improving the rights of European children.