Scottish-born John Baron (1786–1851) was a friend of the famous anatomist Dr Matthew Baillie and the celebrated physician Dr Edward Jenner, who discovered a vaccination for smallpox, and about who Baron wrote a biography. Baron was disabled because of his poor health, described as ‘creeping palsy’, but his mind was unaffected. He promoted the theory that tubercles (small nodules or warts) were hydatids become solid, and although this theory was later discredited, Baron’s theories earned him admission to the Royal Society, where he gained a reputation as a great writer. Baron advocated the more humane treatment of the mentally ill, and was a founder of the Medical Benevolent Fund. This portrait is the only known oil painting of Baron, although engravings exist, at the National Portrait Gallery in London.