Sir Cyril Astley Clarke (1907–2000) led the medical team that discovered how to prevent rhesus haemolytic disease (Rh Disease) of the newborn, one of the major modern advances in preventative medicine. After serving in the navy during the Second World War, Clarke became consultant physician at the David Lewis Northern Hospital in Liverpool. Here he developed an interest in medical genetics following studies of swallow-tailed butterflies. Clarke went on to found the Nuffield unit of medical genetics, which he directed from 1963 to 1972. He was then elected president of the Royal College of Physicians of London, a post he held until 1977. Cyril's work was widely recognised, and he received many national and international awards. The portrait was painted by Ruskin Spear (1911–1990), who, because he used a wheelchair following childhood polio, focused on painting his immediate surroundings in Hammersmith.