A Study in Scarlet is believed to be the first-ever print appearance of legendary sleuth detective Sherlock Holmes, and was first published by Beeton's Christmas Annual for 1887.

It was discovered by two volunteers, Ken Lowe and Rosie Beer, when they were carefully examining a pile of donated books.

The rare classic has now been put up for auction with Bonham's auctioneers in Oxford, where it will show on May 20.

Mr Lowe said: "We saw at once that the book was of great interest – the famous Sherlock Holmes, his first appearance in print, and Beeton's Christmas Annual for 1887.

"We spent a long time checking and researching because the original covers were missing, along with some of the advertisements you expect to find in an annual like this, and the Beeton's did not stand alone. We needed to know how this would affect the value."

"When we were as sure as we could be, we had to decide how best to sell it to maximise profit for Oxfam. We opted for a Bonham's auction in Oxford on May 20, where it would gain national, even international, attention."

Oxfam are given a number of book donations every year, most of which are priced and sold instore or at a nearby shop.

Some books are set aside for further investigation by a team of expert volunteers, and those which are discovered to be of particular interest, rare, originals, or specialised subject, are put up for sale on internet site www.AbeBooks.com.

Rosie and Ken hope that this particular item – their first try at a book auction – will produce a four-figure addition to Oxfam's funds.

All of the books sold at the store in Montpellier Parade, along with music, stamps, old postcards, and cigarette cards, are donated to the store to help raise funds for charitable causes worldwide.