Bonsor was very successful in the brewing industry and rose to chairman of Watney, Combe, Reid & Co. as well as taking a lead role in brewery organisations such as the Institute of Brewing; in 1898 he was elected chairman of the South Eastern Railway and was highly influential in creating a working union between SER and their rivals London, Chatham & Dover Railway (1899); Bonsor acted as chairman of the South Eastern and Chatham Railway until it was amalgamated into the Southern Railway in 1923; 1885-1929 he acted as director of the Bank of England and Northern Assurance Company as well as taking on roles as chairman and treasurer elsewhere; he was created a baronet in 1925 and was Conservative MP for Wimbledon between 1885 and 1900.