BSc (physiology) Manch 1953, MB ChB 1957, MD 1970.
Longson was born on 22 July 1931 and was educated at St Bede's College, University de Louvain and University of Manchester. Longson held house appointments at MRI and Davyhulme Hospital before pursuing a career in clinical pathology. He was resident clinical pathologist at MRI and registrar in pathology at Bolton Hospitals and Radcliffe Infirmary, Oxford. While at Oxford, Longson held a rotating appointment where he assisted Dr F. MacCallum in his polio-virus research programme. This inspired Longson to specialise in virology. In 1963 he was appointed lecturer in virology at the University of Manchester, spending a year of this appointment in France as MRC scholar at the Institut Pasteur. He later became honorary lecturer, probably in the early 1970s when he was appointed consultant virologist to North Manchester Regional Virus Laboratory, MRI, Booth Hall Children's Hospital, St Mary's, Manchester Royal Eye Hospital and the Public Health Laboratories, Manchester. In 1982 Longson was appointed professor of virology at the University of Manchester. Longson was secretary to the working party on herpes encephalitis. He was also a member of council of MMS and a member of the British Society for the Study of Infectious Diseases.