Stephen Howard Powles was born on the 27 July 1900 in Newmarket, Suffolk, England. He was educated at Uppingham, and the Royal Military Academy, Woolwich, and was commissioned in the Royal Field Artillery in July 1919. His unit was posted to the Army of Occupation of the Rhine in January 1920, and later spent a year in Upper Silesia.

In the autumn of 1924 Powles' cousin, Lord Howard de Walden, suggested that he should go to Kenya where he himself was about to buy farming land in the Trans Nzoia, saying that later he might give Powles a small farm. Powles arrived in Kitale, Kenya, in December 1924 and worked as Estates Manager to the Howard de Waldens, father and son, until 1963. During World War II Powles served in the Army (1939-1944).

Powles served on many Committees and Boards between 1934 and 1963 including the Agricultural Production and Settlement Board, the Council of Kenya National Farmers' Union, and the Maize Marketing Board. Public companies of which he was Director (1934-1967) included the East African Standard, Mombasa Times, Tanganyika Standard, Uganda Argus (from 1954), and the Upper Nairobi Township & Estate Company of which he became Chairman.