I would in the first place express my appreciation of the honour conferred upon me by the invitation to deliver the J. D. North memorial lecture, on a subject with which I have been engaged for the past 37 years.
The subject is very wide, covering many types of pumps, and to do it full justice would require far more space and time than can be covered in a single paper. I have therefore attempted to bring out the reasons why we followed certain paths and the problems which caused significant design changes. If I appear to have given undue prominence to the work of the Lucas team, and made insufficient mention of the work of others, I would ask their forgiveness. The pumps used for reheat have been omitted as they are in a field of their own. The future may see a drawing together of the engine and reheat pump practices, although it is too soon to make a meaningful presentation, an indication of the most likely path is shown.