Garry graduated from Sydney University with degrees in Science and Medicine and a PhD in Biochemical Genetics.  After postdoctoral research positions in Oslo and Oxford, he returned to Australia to a lectureship in the Department of Paediatrics in the University of Melbourne and a research position in the Murdoch Institute for Research into Birth Defects in the Royal Children’s Hospital.  During this period, he started to work on Mitochondrial Diseases and, in particular, on pyruvate dehydrogenase and cytochrome oxidase deficiencies. In 1989, he returned to the UK to a lectureship in the Department of Biochemistry in the University of Oxford and a tutorial fellowship at Lady Margaret Hall. He was also appointed an Honorary Consultant in the Department of Medical Genetics at the Churchill Hospital and made a Fellow of the Royal College of Physicians.

In the Biochemistry Department, Garry continued research into various aspects of the biochemistry and genetics of mitochondrial disease, with a particular focus on Leigh syndrome and mechanisms of neuropathology.  In conjunction with the various research projects, his laboratory also provided a diagnostic service for pyruvate dehydrogenase deficiency and the increasing number of genetic defects associated with cytochrome oxidase deficiency.  Since retiring from his University position in 2014, he has moved the diagnostic part of the laboratory to the Oxford Medical Genetics Laboratories to maintain continuity of this service. He continues to teach for the undergraduate medical course, both in College and in the central University.