[1] Campbell-Johnston became involved in Unionist politics, and stood unsuccessfully for parliament in the December 1910 general election as the Conservative candidate at Osgoldcross in the West Riding of Yorkshire.
[1] With the outbreak of the First World War, Campbell-Johnston obtained a commission in the 8th Battalion, York and Lancaster Regiment.
[1] Following the war he attempted to gain election to the London County Council in 1919, standing as a member of the Conservative-backed Municipal Reform Party at Bow and Bromley without success.
Campbell-Johnston was chosen by the Conservatives to attempt to win the seat of East Ham South from the Labour Party, who opposed the National Government.
[8] When the next general election was called in 1935, Campbell-Johnston failed to hold his East Ham seat in a straight fight against Barnes, the man he had defeated four years earlier.