Chiefly in-coming letters, arranged alphabetically by surname of correspondent. The original order of this series is unknown and it is unlikely to have been arranged by HMC herself: however, it appears to form one of the largest single correspondence series in the Cam collection. It has been studied in detail by Barbara Megson, who compiled a sheet of details for each correspondent, giving number of letters, date coverage, subject material of letters, and brief details of the correspondents themselves (eg whether Old Girtonians, Cambridge historians, etc). These sheets are held separately from the letters and may be consulted by readers. A brief analysis of them shows that the series contains approximately 1400 letters from about 650 correspondents. About 90 of these are Old Girtonians, 20 or so are colleagues and contemporaries from Royal Holloway College, a small percentage are purely personal, and the bulk of the remainder are fellow historians and academics.