On 28 July 1714, upon the death of his great uncle Thomas Thynne, 1st Viscount Weymouth, though he was only four years old, he inherited Longleat House and its great estates and succeeded to the Baronetcy of Thynne, of Kempsford, Gloucestershire, and (by special remainder) to the titles of Baron Thynne of Warminster, Wiltshire, and Viscount Weymouth, of Dorset.