After secondary education at the Ipswich Grammar School in Queensland, Charles went on and graduated from the University of Queensland Medical School with honours in 1980. Following graduation Charles completed regional and rural service with the Queensland Department of Health in Cairns, Dirranbandi and the Gold Coast.

In the small western Queensland town of Dirranbandi, where Charles was the medical superintendent for a year, he was also asked to act as the local veterinary surgeon despite protesting that he had no training in the care of animals such as horses and dogs. At least one kelpie dog returned to mustering sheep after falling off a motorbike and subsequently having a leg amputated by the 'temporary' vet.

Charles continued physician training at the Princess Alexandra Hospital in Brisbane in 1984. Later, having been mentored by Professor Paul Kerlin, Charles completed advanced training in gastroenterology and hepatology leading to Fellowship of the RACP in 1988. During 1988, Charles began an appointment as an Australian Fulbright Scholar, with the assistance of an Overseas Travel Award of the RACP, researching gastrointestinal physiology at the Mayo Clinic in Rochester, Minnesota, USA under the mentorship of Professor Sid Phillips. As a Fulbright Scholar, Charles was regarded as being a guest of the USA and was hosted in 1989, with his family and other international Fulbright Scholars, to a week of events in Washington DC including a "handshake meeting" with President George HW Bush on the "White House" lawn and a formal lunch reception at the US Department of State.

While in Rochester, at a young age, Charles was appointed Director of Gastroenterology and Hepatology at the Princess Alexandra Hospital in Brisbane, returning from the USA to take up that position in March 1990. From his combined period of Australian and American research, Charles was awarded a higher doctorate ("Doctor of Medicine" - MD) by the University of Queensland in 1994. At the Princess Alexandra Hospital, Charles became Associate Professor of Medicine with the University of Queensland and transitioned to the position of Senior Visiting Medical Officer in gastroenterology and hepatology. During this time Charles began a private specialist practice in gastroenterology and hepatology at the Mater Private and Greenslopes Private Hospitals in South Brisbane. Later, this lead to Charles becoming a founding director of the large Brisbane private specialist practice, Queensland Gastroenterology.

Charles is a long-standing member, since the 1980s, of the Gastroenterological Society of Australia (GESA) and the Gastroenterological Society of Queensland (GESQ) and was made a life member of the GESQ after his retirement. Charles served on the Scientific Programme Committee of GESA and became Chairman of the Specialist Advisory Committee for Gastroenterology (RACP) for around 6 years overseeing advanced training in gastroenterology and hepatology in Australia under the auspices of the RACP. During this period, Charles was a member of the "Committee for Physician Training" of the RACP. Charles maintained his links with gastroenterology in the USA and was honoured by being made a Fellow of the American Gastroenterological Association (AGAF) in 2012 while also being a member of the American Society for Gastrointestinal Endoscopy.

Charles was a member of the national examining panel (NEP) and later, senior examining panel (SEP) of the RACP in the clinical divisional examinations of the RACP. During this time, Charles was also a medical officer in the Australian Army and saw active military service with the Australian Army in Afghanistan. Rather unusually for physician, Charles became an instructor, with the RACS, in the early management of severe trauma during his period of service with the Australian Army. Charles was also a director of the Medical Indemnity Protection Society Ltd (based in Melbourne), a position he held for approximately 17 years. During this period, after training in corporate governance and becoming a Fellow of the Australian Institute of Company Directors, Charles was appointed a director and Honorary Treasurer of the RACP from 2015 to 2018.

In Queensland, Charles was a member, and for short time before retirement, Deputy Chairman, of the General Medical Assessment Tribunal of the Workers Compensation Regulator of Queensland. Charles is a member of the Queensland Art Gallery Foundation and has been a philanthropic supporter of the Queensland Women's Historical Association in Brisbane. In the Australian Queen's Birthday Honours list in 2021, Charles was honoured by being made a Member of the Order of Australia (AM) for significant service to tertiary medical education and to gastroenterology. Charles is married with three children. He gradually retired from all clinical and other appointments until being fully retired, by choice, on 31 December 2021.

Awards and honours

• Overseas Travel Award of the RACP (1987)
• Australian Fulbright Scholar (1988)
• Australian Active Service Medal (2009)
• Fellow of the American Gastroenterological Association (AGAF) (2012)
• Member of the Order of Australia (AM) (2021)