I graduated in medicine in 1983 and trained in paediatrics in London. I spent the next eight years working in Asia as a clinician  and senior manager for NGOs, WHO and UNICEF. While based in China  I also  worked in Indonesia, the Philippines, Cambodia, Laos and  Myanmar. In China I was the lead on the establishment of the first pediatric and neonatal intensive care units, in the cities of Shanghai, Hangzhou and Xian.  I also led on a nationwide basic neonatal programme. Programmes elsewhere covered immunisation, malaria control, safe motherhood and systems for cost recovery.  I returned to the UK in 1993 and trained in public health in London. I came to the Institute of Child Health as a research fellow. I was awarded a Wellcome Trust Clinical Fellowship in 2000 to explore the epidemiology of HIV, HBV and HCV in China. I was awarded my PhD in 2001. In 2004 I became Associate Professor in the Centre for International Health and Development at the Institute of Child Health and became Professor of Global Health at the UCL Institute  of Global Health in 2008.I was Deputy Director of the Institure of Global Health from 2010 to 2015 and Acting Director in 2015. In 2016 I was asked to establish a Center for Global Health at Zhejiang University in China. I am honorary consultant at Public Health England. I have conducted a number of consultancies for UNICEF, UNFPA, European Union, Public Health England and Save the Children Fund, in the UK, Tanzania, Kenya, Uganda, Egypt, Pakistan, India, UAE and Sri Lanka.