The contribution, history, impact and future of physics in medicine.

This is an "Opinion" or "Commentary" text to support the Invited Opening Plenary Lecture of the NACP2008 Conference. It is an outrageously broad title, that I have been given, and I have made selections for the focus of the lecture and for this report. I observe a research methodology in medical physics whereby key developments have come from standing on the shoulders of those who have come before and I illustrate this by the invention of x-ray computed tomography and the development of intensity-modulated radiation therapy. The equally key role of somewhat maligned incremental science is also discussed. Some commentary is made on the enormous range of activities in medicine to which medical physicists have contributed. Conversely, future gazing is a totally unscientific process. Nevertheless I add my thoughts in broad generalities and also in specifics for the field (radiotherapy physics) in which I work and might be expected to be more accurate in my proposals. I conclude with some remarks on the conditions needed to achieve good scientific outcome.