A rare first edition of Charles Darwin's "On the Origin of Species" is expected to be sold at auction for around £60,000 -- after it was found in a toilet.

The book, one of the first 1,250 copies ever printed, was discovered in an Oxford toilet where it had been left on a shelf.

While going to the loo, the son-in-law of the current owners spotted the On the Origin of Species, and thinking it looked old, gave it a closer inspection.

He then noticed a picture of the spine of the work and as he flipped the book open he realised it was a rare first edition.

At that point (but hopefully after pulling his trousers up) he told the owners who will sell the but at a Christie's auction today.