Simon qualified from the Royal London Hospital Medical College in 1986. As a Wellcome Training Fellow he undertook doctoral study in Clinical Epidemiology and Public Health at the University of Southampton and London School of Hygiene and Tropical Medicine, before moving to the University of Cambridge in 1998. Since 2005 Simon has led the Prevention Group in the MRC Epidemiology Unit, now in its fourth quinquennium. He was appointed Professor of General Practice in 2013.

His research contributes to efforts aimed at preventing the growing burden of diabetes, obesity and related disorders by translating epidemiological knowledge into preventive action, and evaluating the effectiveness of a range of strategies from behaviour change to screening. He has completed 40 trials and authored over 500 publications which have been cited 40000 times (Google scholar h-index: 101), but what he really likes to do is surf.