Professor Stephenson is Chair of the General Medical Council.

He studied medicine at Oxford Medical School and has spent most of his career specialising in paediatric medicine and paediatric emergencies. He was also President of the Royal College of Paediatrics and Child Health and a member of the GMC Council between 2009 and 2012. He is currently Nuffield Professor of Child Health at the Institute of Child Health at University College London, Honorary Consultant Paediatrician at UCL Hospitals NHS Foundation Trust & Great Ormond Street Hospital for Children NHS Foundation Trust, and current Chair of the Academy of Medical Royal Colleges*.