Sir John Lilleyman is a distinguished paediatric haematologist whose principal interests are in leukaemia and in idiopathic thrombocytopenic purpura. He has made major contributions to trials of treatments in child leukaemia and has also carried out original studies on thiopurine metabolism in children with leukaemia. His other main interest has been in childhood ITP where he promotes scepticism about the general early treatment of this disease with intravenous immunoglobulin. In addition to his clinical and research career, John Lilleyman has, for many years, taken a major national role in pathology and medicine in the UK. He was a highly esteemed President of the Royal College of Pathologists and was in this office throughout the Alder Hey episode, which he handled with skill and sensitivity. While PRCPath he was also Vice-Chairman of the Academy of the Medical Royal Colleges and, after stepping down as PRCPath he completed a successful term as President of the Royal Society of Medicine. He now serves as strategic Advisor to the National Research Ethics Service and is a highly distinguished figure in British medicine.