Kaye Wellings is Professor of Sexual and Reproductive Health, and Head of the Department of Social and Environmental Health Research, at the London School of Hygiene & Tropical Medicine (LSHTM). She is a founder of and Principal Investigator on the National Survey of Sexual Attitudes and Lifestyles and she is internationally recognised as an expert in sexual health.Kirstin Mitchell is Lecturer in Sexual and Reproductive Health at the LSHTM. She has lived and worked for extensive periods in Africa and is currently working on the third UK National Survey of Sexual Attitudes and Lifestyles.Martine Collumbien is Senior Lecturer in Sexual and Reproductive Health at the LSHTM. She is a demographer by training with extensive experience of methodological and evaluation research. Her work has a global reach, with a particular focus on South Asia.