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.
At the time of the dissolution of monasteries, official state records and important papers were poorly kept, and often retained privately, neglected or destroyed by public officers. Sir Robert collected and bound over a hundred volumes of official papers. By 1622, his house and library stood immediately north of the Houses of Parliament and was a valuable resource and meeting-place not only for antiquarians and scholars but also for politicians and jurists of various persuasions, including Sir Edward Coke, John Pym, John Selden, Sir John Eliot, Thomas Wentworth.
Such important evidence was highly valuable at a time when the politics of the Realm were historically disputed between the King and Parliament. Sir Robert knew his library was of vital public interest and, although he made it freely available to consult, it made him an object of hostility on the part of the government. On 3 November 1629 he was arrested for disseminating a pamphlet held to be seditious (it had actually been written fifteen years earlier by Sir Robert Dudley) and the library was closed on this pretext. Cotton was released on 15 November and the prosecution abandoned the following May, but the library remained shut up until after Sir Robert’s death; it was restored to his son and heir, Sir Thomas Cotton, in 1633.