Sir William Overend Priestley (1829–1900) was a great-nephew of Joseph Priestley, who discovered the element oxygen. He was a gifted medical student, and his papers attracted the attention of the famous physician Sir James Young Simpson. Priestley became Simpson’s assistant before moving to London and becoming a lecturer in midwifery at Middlesex Hospital. Priestley married the daughter of Robert Chambers, of the famous publishing firm, and was subsequently accepted into society. His wealth and connections helped him establish a very successful practice and he retired at the age of 43. He became physician-accoucheur to Princess Alice of Hesse and Princess Christian of Schleswig-Holstein, and was knighted in 1893. The portrait is by the German-born British portraitist and author August Wilhelm Rudolf Lehmann.