Muir Gray entered the Public Health Service by joining the City of Oxford Health Department in 1972 after qualifying in medicine in Glasgow, the city of his birth

When he asked his first boss, the Medical Officer of Health of the City of Oxford, what he wanted him to do the MoH gave him the perfect answer “what do you think needs to be done?” to which he replied that no-one seemed even to know how many older people there were in the City so the MoH told him to get a grip of Population Ageing. Since then this has been his continuing interest but he has had other responsibilities.  The first phase of his professional career focused on disease prevention, for example on helping people stop smoking. Then he developed all the screening programmes in the NHS, for pregnant women, children, adults and older people using systems theory. He set up a national programme   www.livelongerbetter.uk and published a number of books. For professionals he published Our Elders in 1981 and the first ever book on Prevention of disease in the Elderly in 1985. For the general reader he published Sod60! With Claire Parker, Sod70! on how to increase healthy life expectancy in the 70s, 80s and 90s and How to Increase Your Brainability and Reduce Your Risk of Dementia. He has also published a book on the science of living better for longer titled The Antidote to Ageing. He is the director of  the Optimal Ageing  Programme at Oxford

He started work on value in the NHS in 2003 on Value based Healthcare and published the first Annual Population Value Review for the Department of Health in 2004 and the first NHS Atlas of Variation, modelled on the Dartmouth Atlas of Healthcare, in 2010.He now is a director of the   Oxford Value and Stewardship Programme  and has published a series of How To Handbooks for example, How `to Get Better Value Healthcare first published in 2007, How to Build Healthcare Systems and How to Create the Culture of Stewardship

He was awarded both a CBE and later a Knighthood for services for the NHS.