In the 1930s, Kerr served as Parliamentary Private Secretary to Alfred Duff Cooper, starting in 1933 when Cooper was Financial Secretary to the War Office. During the Second World War, he served in a balloon squadron in the Royal Air Force and briefly held office as Parliamentary Secretary to the Ministry of Health in the 1945 caretaker government.
Kerr's career involved working with Alfred Duff Cooper, starting as his assistant in the War Office and later as a member of the Ministry of Health. During World War II, he was part of the Royal Air Force.