A special collection of documents (some transferred from SP 59) particularly concerning Mary, Queen of Scots from her flight from Scotland into England in 1568 until her execution in 1587. Thus the records span only part of Elizabeth I's reign.
The series contains correspondence between the Queen Mary and Queen Elizabeth, their ministers and representatives, not least Mary's custodian's evidence of Mary's and her supporters' machinations, including her 'casket letters' to the Earl of Bothwell, her third husband, and, above all, the papers seized at Chartley Castle on the discovery of the Babington conspiracy in 1586 which were used, when deciphered, to implicate Mary and bring her to trial.
The series includes a collection of over 100 ciphers, most of them used in communication with Mary. and used to decipher calendared letters. Different ciphers were used by the Queen's correspondents. Some of these correspondents are identified, but some remain 'anonymous'.