I have spent the last 30 years researching the economics of health systems in low- and middle-income countries. My major contributions are in the areas of health financing and the private health sector. I chaired the recent Lancet Global Health Commission on Financing Primary Health Care, and have authored key publications on how strategic purchasing can help to improve health system performance. My work on the private sector has contributed to our understanding of the opportunities and limitations of using the private sector to extend access to critical public health interventions and, more recently, to the challenges of regulating healthcare markets. I frequently advise national governments and international organisations on health system and financing issues. I am President of the International Health Economics Association, and Director of the NIHR Global Health Research Programme