 A noted agricultural expert, he was on the board of the Irish Agricultural Organisation Society (IAOS) from 1912 where he remained until 1927 with the noted reformer Sir Horace Plunkett.He was elected to the Irish Free State Seanad in 1922 for Cumann na nGaedheal, where he was part of a parliamentary Commission to broker peace in the Irish Civil War.He was elected as Leas-Chathaoirleach to Lord Glenavy in 1925 and as Cathaoirleach (Chairman) of the Senate in 1928, he was vigorous in defending constitutionalism in Irish life during a turbulent time and was engaged in a very high-profile contest with the President of the Executive Council Éamon de Valera in 1935 during the campaign to abolish the Seanad, in which he was assisted by his brother George C. Bennett, a Teachta Dála (TD) in Fine Gael and later Senator.