John Macleod is Professor of Clinical Epidemiology and Primary Care, Director NIHR Applied Research Collaboration West (ARC West), Co-lead Centre for Academic Primary Care and NIHR School for Primary Care Research, University of Bristol. John’s main epidemiological research interests are the explanation and amelioration of health inequality with a particular focus on the role of factors acting in earlier life and the use of routine data in epidemiological research. Clinically his research has focused on the treatment of substance use in the community and on screening and treatment for Chlamydia in primary care. He is a co-director of the Avon Longitudinal Study of Parents and Children and leads a Wellcome Trust funded programme developing methods to follow-up population-based cohorts through linkage to administrative health and social data.