Sir Thomas Duffus Hardy (1804–78) was Deputy Keeper of the Public Record Office. He was closely involved with the Rolls Series of publications of medieval manuscripts in public ownership, of which this catalogue (consisting of three volumes in four parts) forms part. His stated aim was to list 'all the known sources, printed or unprinted, of English history'. 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. The third volume, published in 1871, provides historical sources ranging from 1200 (the first full year of King John's reign) to the death of Edward II in 1327. This volume features 20 plates illustrating some of the types of manuscripts catalogued. A fourth volume, left uncompleted at Hardy's death, was to have continued the catalogue to the end of Henry VII's reign (1509).