During his
pre-registration year, 1957, Chamberlain remained at
St Bartholomew's Hospital. He first undertook a nine-month appointment as house physician then three months as a house surgeon. His career direction in medicine rather than surgery was confirmed by a disastrous house surgeon rotation. He had been described by his surgical supervisor as the worst house surgeon he had ever encountered. He was promoted to
captain (acting Major) on 5 January 1960 and posted to BMH Hostert in Rheindahlen. After a short spell working in chest medicine at the
Brompton Hospital, Chamberlain returned to Cardiology at St Bartholomew's in January 1962 as a research Registrar and at the end of the tenure was promoted to Senior Registrar in December 1966. He served 2 years of the 4-year posting before taking a year's fellowship in
Massachusetts General Hospital in 1968 working within the orbit of the Cardiac Catheterization Laboratory, a subdivision of the Department of Cardiology before returning for a final year at St Bartholomew's. Much of his research centred around the sympathetic nervous system, beta-blocking drugs, and pacing. He worked at the
Royal Sussex County Hospital between 1970 and 1991 as a
Consultant Cardiologist, and as Honorary Consultant subsequently. Chamberlain, together with
Peter Baskett, trained ambulance personnel in
resuscitation from late 1970. This was a pivotal moment in the development of the paramedic profession and Chamberlain and Baskett's work here and subsequently are acknowledged as the naissance of paramedics in Europe. Paramedics are now acknowledged as an autonomous and regulated profession and are still recognized for their abilities in cardiac care - as was first discovered by Chamberlain when teaching ECG recognition and cardiac care to nurses, doctors and ambulancemen from the 1970s to the mid-1990s in Brighton. During this period, Chamberlain developed his "10 Rules of a normal ECG", a foundation for ECG interpretation used all over the world to this date. Chamberlain maintained a major interest in resuscitation and prehospital care, and played a role in the development of the
European Resuscitation Council and the International Liaison Committee on Resuscitation. Well into his 80s, Chamberlain was an Honorary Advisor to
South East Coast Ambulance Service NHS Foundation Trust and
London Ambulance Service NHS Trust and was 'available any time of the day or night to take calls from paramedics'. He co-edited
Cardiac Arrest: The Science and Practice of Resuscitation Medicine, a reference book on advanced life support and resuscitation medicine. It was winner of the 2008 British Medical Association prize in Cardiology. He was Editor Emeritus of
Resuscitation, the official journal of the European Resuscitation Council, and was author or co-author of over 200 papers. Chamberlain died on 22 May 2025, at the age of 94. ==Honours==