Booklovers around the world have been helping investigators trace thousands of rare volumes that were looted from one of Italy’s oldest libraries. The shelves of the Girolamini Library in Naples once held works of extraordinary value: a 1518 edition of Thomas More’s Utopia, Galileo’s 1610 treatise Sidereus Nuncius, containing more than 70 drawings of the moon and the stars, and Johannes Kepler’s study of the motions of Mars, Astronomia Nova, described as one of greatest books in the history of astronomy.

But over the past year, this magnificent piece of Italy’s cultural heritage was methodically plundered by a gang of thieves which included the librarian himself.

The looting of the collection was only discovered when Tomaso Montanari, an art historian, visited the library (which is closed to the public) by chance last March. He was horrified to find books strewn around the floor and empty Coca-Cola cans and other rubbish littering the wood-panelled library. After the authorities were notified, a large-scale investigation was launched and to date, about 80% of the stolen tomes have been recovered.