Barry studied at the University of Edinburgh, and received his qualification as a doctor of medicine in 1812, when he would have been about 19 or 20 years old (or 10, according to his own account of his age!). After this, he studied in London and qualified as a surgeon in 1813.

He proceeded to join the British army, enlisting as a hospital assistant just four days after qualifying as a surgeon. During his 46 years of service, he gained huge renown as a surgeon and a doctor.

In 1816, Barry went on his first overseas posting as an assistant surgeon. He was posted to Cape Town, and quickly became friends with the governor, Lord Charles Somerset. The friendship began because Barry treated Somerset's sick daughter spectacularly well.

Later in his life, in 1829, Barry went absent without leave from the army when Somerset himself became sick. He spent two years treating his friend until Somerset's death.

In 1822, Somerset promoted Barry to the role of Colonial Medical Inspector, which was an astronomical leap in Barry's career.

Sometimes, though, the friendship raised eyebrows. In 1824, Somerset and Barry were accused of having sex with each other.

One of his most famous arguments was with Florence Nightingale herself during the Crimean War. When writing about it, years later, Nightingale doesn't specify the cause of the argument, but Barry lived rent-free in her head following it.

Barry's patients loved him, though. As well as being a talented physician and surgeon, he reputedly had a good bedside manner.