Seventy years ago, the Scottish epidemiologist Jeremy Morris published his seminal papers in exercise epidemiology, providing evidence of the positive relationship between physical activity levels and reduced mortality. Today, we may remember Morris's pivotal role in establishing physical activity as a key factor in preventive medicine and public health. The roots of the role of behavioural epidemiology in modern public health lay in Morris's research on the association of coronary heart disease with physical activity at work. In consequence, a new focus for public health emerged, with an emphasis on chronic disease as well as modification of lifestyle and individual behaviour. While the immense value of his research on the health benefits of exercise is widely recognised, his influence on the teaching of social medicine is generally less well-known. Morris was involved in the pioneering course of MSc in Social Medicine at the London School of Hygiene, which was emblematic of the redefining of public health in the late 1960s. Morris gave legitimacy to a wide range of issues regarded at that time as soft and second class, including health promotion, sociology and the care of people with disability and chronic conditions. In consequence of his observation of a relationship between socioeconomic status and individual behaviour patterns in regard to exercise, nutrition and smoking, Morris urged that greater attention be paid to inequalities.