 He succeeded his father in 1740, inheriting his estates, which included Christchurch Mansion in Ipswich.Returned for Sudbury in 1741, he continued to sit for that constituency until 1768, several of those years in conjunction with Thomas Walpole, a business connection.However, he retained interests in Suffolk and was a member of the Free British Fishery Society, as well as MP for the constituency of Aldeburgh at the end of his life, serving briefly alongside his brother, Zachary Philip Fonnereau.