Born at Easington, Co Durham, where his father was the local doctor, he was educated privately in Durham, then at Rutherford College, Newcastle and at Durham University College. After qualification he served in the RAMC in Mesopotamia as a battalion medical officer. On his return to civilian life he served as surgical registrar at the Royal Victoria Infirmary, Newcastle, where he was later appointed assistant surgeon and in due course surgeon. He was also surgeon to Leaholm Hospital, Easington, originally a general practitioner hospital, but with the coming of the NHS taken over and enlarged by the Sunderland Regional Board. After his retirement he did occasional spells of duty as a general practitioner in Easington. In his leisure he was an ardent trout fisher on the Wear and South Tyne. Hewitson was fond of walking and would go searching for golden eagles. He died at Easington on 7 November 1962 survived by his widow and son, also a Fellow of the College.