 Thomas represented Calne unopposed until 1774, when he moved to Chipping Wycome, another rotten borough controlled by his brother, exchanging seats with Barré.However, whereas William eventually became Prime Minister of Great Britain, Thomas Fitzmaurice had left Parliament by 1780, replaced in Chipping Wycome by Charles Stanhope.In 1776 Fitzmaurice bought the Lleweni Hall estate in Denbighshire from Sir Robert Cotton for £110,000, where he established a large, Palladian-style factory, long, to bleach linen from his Irish estates.