Born Rathdrum, County Wicklow, Ireland, King was largely self-taught as an artist. He had his first one-man show in 1959, but worked as a businessman and did not become a full-time artist until 1964. While he began painting in an expressionist style, his mature works have a distinctive cool minimalist formality and often involves clean blocks of even colour cleaved at an acute angle. The break came in the late 1960s. He lived for many years in Blackrock on Idrone Terrace.