Sir William Stewart is President of the Royal Society of Edinburgh and Chairman of the Microbiological Research Authority. He served as Chief Scientific Adviser to the Prime Minister and to the Government (1990–95). He is a biologist by training. He is Chairman of Tayside University Hospitals NHS Trust. He was the first Head of the UK Government's Office of Science and Technology and has served on various advisory committees including the Royal Commission on Environmental Pollution and the Natural Environment Research Council. He was Chief Executive of the Agricultural and Food Research Council and is a former Vice-President of the Royal Society of London.