He qualified as a doctor from the same month the National Health Service began. In 1962, he took up the chair of surgery at the Westminster Hospital, a post which he held until his retirement from practice in 1989. After a stint teaching anatomy in the University of Cambridge, he took up his present position in 1993. In 1986 he delivered the Bradshaw Lecture on the subject of cancer. The Professor Harold Ellis Medical Student Prize For Surgery has been awarded by the Royal College of Surgeons since 2007. The International Journal of Surgery has awarded the Harold Ellis Prize in Surgery annually since 2003. Ellis, Harold and Mahadevan, Vishy. Clinical Anatomy: Applied Anatomy for Students and Junior Doctors. Oxford: Wiley-Blackwell. ISBN 978-1-1183-7377-4. Ellis, Harold, Calne, Sir Roy Yorke and Watson, Christopher. Lecture notes on general surgery. Oxford: Blackwell Scientific. ISBN 978-1-4051-3911-3.