As a keen club runner, who had represented his university, and a cardiologist, he was recruited to set up medical support for the first London Marathon in 1981, and stayed as unpaid Chief Medical Officer for 27 years. He gave strong support to the concept that the race should be open to public entry, not just to professional or amateur specialist runners and countered opposition based upon concern regarding the risks. As a result, principles were established to keep safe all participants, irrespective of their sporting background; these have been adopted internationally. In addition, Tunstall Pedoe gained funding to establish the
London Sports Medicine Institute at St Bartholomews Hospital. He concluded his London Marathon tenure with a pair of medical journal articles summarizing key aspects of the experience. As well as an amateur runner, Tunstall Pedoe was also a keen astronomer, chess player and amateur photographer, specialising in
macro pictures of wildlife. His photographic work was displayed in health centres in Hackney. ==Death==