The Chained Library, which is really a library of books chained to shelves, is located inside the Hereford Cathedral in Hereford. It’s one of the oldest examples of a security system which dates back to the middle ages. Needless to say, it was highly effective. Today the Chained Library can still be seen as it was ages ago, maintained in state-of-the-art environmental conditions designed to preserve more than 229 medieval manuscripts. The library is also home to more than 1,500 rare books and documents from the 8th to 19th centuries, including the Magna Carta 1217. The oldest book in the collection is the Hereford Gospels, circa 800. You can learn more about the library here.
The short video clip below is from a PBS series on the history of the computer, the segment about Chained Libraries.