Born at Westcombe Park, Blackheath on 9 June 1883, the only son of A G Mackenzie, FIA, and Beatrice E Dell, his wife. He was educated at Eastbourne College, at Emmanuel College, Cambridge, where he graduated after obtaining a third class in the Natural Sciences Tripos, Part I, and at the Middlesex H

Born on 18 January 1884 he was educated at Sydney Grammar School, matriculating in 1901. Early in his medical course he showed his interest in practical work and shared the Haswell Prize for practical biology, winning the John Harris scholarship in his third year. He was top in the fourth and fifth