Professor David Leon is a distinguished epidemiologist at the London School of Hygiene & Tropical Medicine (LSHTM), where he leads the Department of Non-Communicable Disease Epidemiology and co-chairs the institution's Ethics Committee. His academic journey began with a degree in sociology and philosophy, transitioning into epidemiology in the late 1970s. He joined LSHTM in 1985, focusing on occupational cancer and socio-demographic disparities in cancer incidence, notably through the pioneering ONS Longitudinal Study