Three "rare" Harry Potter first editions that were found in a skip 12 years ago are expected to sell for thousands at auction.
Two paperback versions of Harry Potter and Philosopher's Stone and one hardback are going up for sale in May.
The seller rescued them when a school was throwing tatty books away in preparation for an Ofsted inspection.
Derbyshire auctioneer Hansons says hardback first editions of the book are "as rare as hens' teeth".
The 65-year-old owner from Buckinghamshire - a teacher who did not want to be named - said when she saw the books in the skip "it just seemed awful to throw them away".
"I had no idea they were of any value, and neither did the school," she said. "They'd been well-read and the school always ensured its library was pristine for Ofsted inspections."
The books ended up in her loft, but four years ago her son investigated their value.
The seller said: "A London business offered £4,000 for one of the paperbacks there and then, but they just went back into the loft.
"Last year we were watching a TV interview with Charles Hanson, owner of Hansons Auctioneers, about the sale of a Harry Potter first edition which sold for thousands at auction and decided to get in touch."
Hansons book expert Jim Spencer said: "Hardback first editions of Philosopher's Stone are as rare as hens' teeth. They're the holy grail for collectors."
There were 500 hardback first editions of Harry Potter and the Philosopher's Stone printed in 1997.
Three-hundred of the books were sent to British schools and libraries and others were sent to private book shops.
All of them contain printing errors, which were corrected in later versions.
The hardback is expected to sell for between £8,000 and £12,000, and the two paperbacks are expected to fetch £2,000 and £3,000 each in the Potter-themed online-only auction on 21 May at Bishton Hall in Staffordshire.