The collection focuses on two members of the Lally-Tollendal family: Thomas-Arthur, Comte de Lally, Baron de Tollendal (1702-1766) and his son Trophime-Gérard, marquis de Lally-Tollendal (1751-1830). It comprises of ca. 440 letters, notes, and 1 scroll with metal container and wax seal. Much of the collection concerns the confiscation of Thomas-Arthur's estate by the French authorities arising from his conviction of treason (and subsequent execution) for alleged military failings in Pondicherry, India and the protracted efforts of his son to have this sequestration lifted as part of a broader endeavour to clear his father's name. The collection also concerns the emigration of Trophime-Gérard from revolutionary France, his related quest for recognition as a subject of both Britain and France, and his claims and interests in Ireland and France. A number of documents focus on Lally family history and reference prominent figures including James and Gerard Lally.