ALEX MOLD is a lecturer in history at the London School of Hygiene and Tropical Medicine. She is also the author of Heroin: The Treatment of Addiction in Twentieth Century Britain, published by Northern Illinois University Press in 2008. VIRGINIA BERRIDGE is Professor of History at the London School of Hygiene and Tropical Medicine and Director of the Centre for History in Public Health. She is the author of books and articles on the history of health with a focus on drugs, other substances, public health and health policy.