Cotton Library

The Cotton or Cottonian library was collected privately by Sir Robert Bruce Cotton MP (1571–1631), an antiquarian and bibliophile, and was the basis of the British Library. After the Dissolution of the Monasteries, many priceless and ancient manuscripts that had belonged to the monastic libraries began to be disseminated among various owners, many of whom were unaware of the cultural value of the manuscripts. Cotton's skill lay in finding, purchasing and preserving these ancient documents. The leading scholars of the era, including Francis Bacon, Walter Raleigh, and James Ussher, came to use Sir Robert's library. Richard James acted as his librarian. The library is of especial importance for sometimes having preserved the only copy of a work, such as happened with Beowulf and Sir Gawain and the Green Knight.

More information on the Wikipedia page.