LONDON: A first edition of Charles Darwin's seminal On the Origin of Species will be sold this week after it was found in a family's toilet in southern Britain, an auction house said on Sunday.

The book, which was first printed in 1859, was bought by a family for just a few shillings in a shop about 40 years ago, Christie's auction house said.

The family has since kept the work on a bookcase in the guest lavatory at their home.

The book will go under the hammer in London today, to coincide with the 150th anniversary of the publication of the father of the theory of evolution's famous work.

The book, about 1,250 copies of which were first printed, is expected to fetch $99,000.

Margaret Ford, head of books and manuscripts at Christie's, said the last buyer "maybe did not know how much of a bargain he was getting."

Christie's said the son-in-law of the current owners was at an exhibition on Darwin and spotted a picture of the spine and realized the book in the toilet had a binding that matched the picture.