Born in 1920 the second son of W H Trethowan, his elder brother, another W H Trethowan (FRCP), is Professor of Psychiatry at Birmingham University, his maternal great-uncle, HE Durham, and his father before him, A E Durham, were all Fellows of the College and at Guy's Hospital. He was educated at The Hall School, Hampstead; Oundle School and Clare College, Cambridge, and then proceeded to Guy's Hospital for his clinical training. After qualifying in 1943 he held house appointments at Guy's and the EMS Sector Hospitals. His registrarships were held at the North Staffordshire Royal Infirmary and Guy's Hospital where he was senior registrar from 1951 to 1954 and came under the influence of E G Slesinger. In 1954 he was appointed a consultant ENT surgeon to the Kent and Sussex Hospital. He also was a member of the Deaf Children's Assessment Panels for mid-Kent and East Sussex. In 1948 he married Kathleen Isitt, who was a State Registered Nurse and they had two daughters, Jane and Tiggi, and one son, Hugh, none of whom are following medicine. He died on 10 March 1989 survived by his wife and family.