A 'Holy Grail' first edition of The Hobbit is set to sell for thousands at auction - after being discovered during a routine house clearance.

The copy of J. R. R. Tolkien's 1937 work was discovered tucked deep into an old bookcase at a home in Bristol.

It is one of only 1,500 copies initially printed in September 1937.

Such was its popularity that within weeks all copies had been sold and a second printing was undertaken.

The surviving books from the initial print run are now considered some of the most sought-after in modern literature.

It's expected to fetch over £10,000 when it is sold by Auctioneum Ltd., an auction house in Bristol and Bath, later this month.

The auctioneers said the original owner had passed away and they had been called in to assess the contents.

Book specialist Caitlin Riley said: "Nobody knew it was there. It was just a run-of-the-mill bookcase, containing the usual reading and reference books you'd expect to find. "

"It was clearly an early Hobbit at first glance, so I just pulled it out and began to flick through it, never expecting it to be a true first edition."

Caitlin added: "I couldn't believe my eyes. There are a few key details to look out for when spotting one of the first editions, and as I looked into each one, they were all there. "

"When I realised what it was, my heart began pounding. It's an unimaginably rare find."

The book had come from the family library of Hubert Priestley, a famous botanist in the 1930s, and brother to Antarctic explorer and geologist Sir Raymond Edward Priestley.

Priestley had strong connections to the University of Oxford where Tolkien was the Rawlinson and Bosworth Professor of Anglo-Saxon and a Fellow of Pembroke College, Oxford.

Both shared mutual correspondence with fellow author C.S. Lewis, and it is likely that both men knew each other.

The first edition is bound in light green cloth and features black and white illustrations by the author; the only printing to do so, as later editions colourised them.

"The popularity of The Hobbit has only grown since its first publication," adds Caitlin. "

"The book was published to huge critical acclaim, and is one of the best-selling stories of all time. "

"The subsequent Hobbit film series in the mid-2000's only further cemented its appeal, and brought the tale to a whole new audience. "

"We're expecting world-wide demand for this rare first edition."

First edition, first impressions of The Hobbit rarely come up for auction. Out of the 1,500 printed, only a few hundred are believed to still remain.

This example carries a pre-auction estimate of £10,000 to £12,000 and goes under the hammer in Auctioneum's Books & Works On Paper Auction on August 6th.

The full catalogue can be viewed on their website www.auctioneum.co.uk.