Christie's are to sell a first edition copy of Darwin's celebrated text on November 24 which has recently turned up in Oxford.
The book had been resting conveniently on a bookshelf in a family's second lavatory, having been owned by them for four decades. Its worth only came to light when it was recognised by the buyer's son-in-law as resembling one from an exhibition.
Still in its original green cloth with gilt-decorated spine, though lightly bumped at the edges, the work is expected to sell for £40,000-£60,000 (up to $99,480). The owner may be forgiven for not recognising the value, as they bought it for a few shillings in a West Country bookshop.
Only 1,250 copies of the work were produced in 1859. The second edition had the phrase "by the Creator" added to the last sentence.
Items associated with Darwin have been in demand this year, which is the 150th anniversary of the Origin of Species' publication. Tomorrow's auction will coincide with the exact date.
A damaged copy of the work sold for £35,000 in Norfolk early in the year, whilst a letter from Darwin fretting about the text being published in America before he could make corrections sold for an estimate-busting £21,000.
Even a whale's tooth carved whilst on Darwin's famous voyage on the HMS Beagle sold for $67,000.
The Oxford copy of On the Origin of Species by Means of Natural Selection will sell in Bond Street, London.