Sir Thomas Duffus Hardy (1804–78) was Deputy Keeper of the Public Record Office and an experienced medieval manuscript scholar, having edited the Monumenta historica Britannica after his mentor Henry Petrie's death. Hardy was closely involved with the Rolls Series of publications of medieval manuscripts in public ownership, a government-backed project, of which this catalogue (consists of three volumes in four parts) forms part. His stated aim was to list 'all the known sources, printed or unprinted, of English history' in a handbook for historical researchers. Each item is located and described, and, where Hardy has examined the original, the first and last lines are given. Where known, the author's life is briefly outlined. Volume 2, published in 1865, provides historical sources for the period between the Norman Conquest and the first year of the reign of King John. It also includes an index for the first and second volumes.