Born the son of C. H. Chapple and educated at Haileybury College, Chapple undertook National Service and was commissioned as a second lieutenant in the Royal Artillery on 3 June 1950. He went to Trinity College, Cambridge in October 1951 and, while still at University, was transferred to the King's Regiment as a second lieutenant on 4 December 1952, and to the South Lancashire Regiment also in the same rank on 20 October 1953. He became a lieutenant in the South Lancashire Regiment on 27 May 1954 and, on leaving University, was transferred to the 2nd King Edward VII's Own Gurkha Rifles (The Sirmoor Rifles) on 3 August 1954 retaining his rank as a lieutenant.