Aviation pathology Mason completed his
internship at Barts, then joined the Royal Air Force in 1943 and served as a medical officer with a fighter squadron with for the remainder of
World War II. He was given a permanent commission after the war and was appointed a Specialist in Pathology in 1951. In 1955, the Royal Air Force (RAF) Department of Aviation Pathology with Mason leading this. He gained a
MD in 1961 with his thesis titled
Aviation pathology : a study of fatalities arising from military aviation in peacetime His book
Aviation Accident Pathology: A Study of Fatalities was published in 1962, and was partly derived from his work while in charge of the institute. He was seconded to
Armed Forces Institute of Pathology in
Washington, D.C. and worked there 1963 to 1965. He retired from the RAF in 1973 at the age of 53.
Regius Chair of Forensic Medicine In March 1973, Mason was appointed to the Regius Chair of Forensic Medicine at the University of Edinburgh, to take up the post in August. His inaugural lecture was given on 28 February 1974 with the title
Ambitions for a Motley Coat. In 1983, the first edition of Mason and
Alexander McCall Smith's Law and Medical Ethics was published. After forty years the book was in its twelfth version.
Biomedical ethics Mason had a "third career" as an expert in
biomedical ethics and was an Honorary Fellow of the School of Law, in addition to being Regius Professor at the University of Edinburgh. In 1998 his book
Medico-legal Aspects of Reproduction and Parenthood was published. ==Awards and honours==