In 1946 he was appointed Assistant Lecturer at the Galton Laboratory at University College London. He remained at UCL for the rest of his career, becoming successively Lecturer and Reader, before appointment as Weldon Professor of Biometry in 1964. On his arrival at UCL, Smith was influenced by J. B. S. Haldane, who introduced him to problems of linkage in human genetics in which field he was able to bring his skills as a statistician to bear.