The son of Humphrey St. John-Mildmay; educated at Christ Church, Oxford, he was a magistrate for Kent and Herefordshire and was a Liberal MP for Hereford (1859-65).

CORRESPONDENCE OF Humphrey Francis St. John Mildmay:

Sydney Smith to Humphrey Francis St. John Mildmay, 30 April 1837 in A Memoir of the Reverend Sydney Smith. By his Daughter, Lady Holland. With a Selection from his Letters, edited by Mrs. Austin 2 vols (London: Longman, Brown, Green, and Longmans, 1855)