Garry Stewart took a degree in Engineering at Cambridge and stayed on to work on scanning electron microscopes. He then spent 10 years at the local company, Cambridge Scientific Instruments, as technical director. He was responsible for the research and development work on electron optical instruments and other products.

He worked for DeBeers for 30 yrs. He built up and managed the UK research lab for the Gem Diamond division. Part of the work was to design and manufacture equipment for automatically sorting and working diamonds.

He is interested in the technologies involved in improving energy efficiency and reducing the consumption of carbon fuels.