John Walsh is a doctor who trained in surgery and orthopaedics before setting up his medico-legal practice. He has written about medicine, though he is also interested in Australian history more broadly. He has researched and written A Brief History of Australian Banknotes, in which he traces the emergence of our currency system. In researching the book, he became interested in the lives of enterprising people including Mary Reibey, who rose from convict origins to become an enterprising and well-respected member of the NSW community.