When the Second World War started, she was appointed to a post at the Samaritan Hospital. From 1947 she ran a mobile obstetric team from University College Hospital. Barnes was the first woman consultant obstetrician and gynaecologist at
Charing Cross Hospital (1954) and the first woman President of the
British Medical Association (1979–80). She was also Chairman of the
Elizabeth Garrett Anderson Hospital Appeal Trust, President of the Association of Chartered Physiotherapists in Obstetrics and Gynaecology (known since 1994 as the Association of Chartered Physiotherapists in Women's Health) from 1977 to 1995, and President of the
Royal British Nurses' Association. She took a prominent role in the public debate over the
1967 Abortion Act. In 1988, she became president of the
Osler Club of London. In 1994, she delivered the Hunterian Oration at the
Hunterian Society. Between 1995 and 1996, Barnes was president of the
History of Medicine Society at the
Royal Society of Medicine. ==Marriage==