Duncan McMillan, mechanical engineer, trained at the Royal Technical College, Glasgow, and at engineering works and became an associate member (later a member) of the Institution of Mechanical Engineers. He came to South Africa in 1910 to take up the post of lecturer in mechanical engineering at the South African College, Cape Town, and proved to be a good teacher. He became the leading technical expert in South Africa on automobiles, wrote a textbook on The motor car (London, 1915), edited the periodical Motoring in South Africa, and wrote numerous articles for it.
In February 1916, during World War I (1914-1918), McMillan obtained leave to do military service in East Africa. After the South African College became the University of Cape Town in 1918 he was promoted to professor of mechanical engineering in 1919, a post he held to his retirement in 1954, by which time his department was rather outdated. He also served on the council of the Cape Town Technical College for 30 years. In 1929 he and J.G. Rose* contributed a paper on 'Alcohol mixtures as motor fuels in South Africa' to the South African Journal of Science (Vol. 26, pp. 29-38). McMillan delivered this paper at the joint meeting of the British and South African Associations for the Advancement of Science in South Africa in 1929. He also served as joint local secretary of Section G (Engineering) of the British Association at this meeting.