A first edition of Charles Darwin's 'On the Origin of Species' has been sold at Christie's.

The book, which was bought about 40 years ago in a West Country shop for a few shillings, made £103,250 in the auction in November 2009.

The book has been kept on a shelf in a lavatory at the owner's family home in Oxfordshire as part of the 'Loo Literature'.

Just 1,250 copies of the work were produced in 1859 and the book was sold exactly 150 years to the day after its first publication.

Christie's auction house said the son-in-law of the current owner was at a Darwin exhibition and recognised a picture of the book's spine.

Margaret Ford, head of books and manuscripts at Christie's, said the person who bought the book may not have realised its value.

She said: "It's incredibly important. He knew it [the book] was textually important.

"He maybe did not know how much of a bargain he was getting."

The revolutionary scientific work, which has the full title On the Origin of Species by Means of Natural Selection, has the original publisher's green cloth cover and gilt-decorated spine.