As I look back on a long life, I am impressed with how lucky I have been, in all sorts of ways: to have been born with a good outfit of genes, in relation to both physical health and the capacity to work hard; to have had a fascinating childhood; to have had a wartime experience that led me to an interest in infectious diseases as well as to the woman who became my wife; to have as mentors two of the greatest microbiologists of the twentieth century; to have the opportunity to set up a department in a new research university in the fifties and sixties, when Australian universities received their best support ever; to have become deeply involved in one of greatest projects in the history of public health, WHO's Intensified Smallpox Eradication Programme, and to have had support at home and at the university that has allowed me to go on writing papers and books on scientific subjects for twenty years after my formal retirement.