Preface: This book is not an autobiography. It is primarily the history I of my association with the development of the turbo-jet engine in Great Britain. I have included a very brief account of my life prior to my practical work on the turbo-jet engine, in order that the reader may have some idea of the nature of the soil in which the seed of an idea took root and flourished. I have been unable to resist the temptation to include a certain amount of "There I was, upside down, nothing on the clock, and still climbing" sort of thing, partly because I hope it will help to lighten a somewhat heavy theme, and partly because I do not like people to forget that at one time I had some skill as a pilot. This material is not entirely irrelevant, because I have always held that my experiences as a pilot contributed immensely to my work on the jet engine. This is not a technical book—or at least it is not intended to be—and I hope that it will be reasonably comprehensible to the lay reader. The nature of the subject, of course, makes it necessary to include a small amount of technical matter, but I have done my best to keep this down to an absolute minimum, yet I still feel a little uneasy lest it should fall between two stools-too non-technical for the engineer and scientist and a little too technical for the lay reader. I have been too close to the technicalities of my work for too long for it to be possible for me to see the book from the lay readers' point of view. My attempt to keep the book non-technical has another disadvantage—our long and bitter struggles with engineering problems receive far less prominence in the narrative than would be appropriate in a balanced history, and the reader may well get the impression that I spent far more time arguing, and writing controversial letters than working on the engine development itself. This, of course, is quite wrong- the truth is that by far the greater proportion of my time was concerned with engine design, manufacture, test-ing, analysis of test results, and many other engineering aspects of the development. Perhaps some day it may be possible to write a detailed technical history to supplement the present record. Those who would like to know more of that part of the story now are referred to the First James Clayton Lecture which I delivered to the Institution of Mechanical Engineers on October sth, 1945, entitled "The Early History of the Whittle Jet Propulsion Gas Turbine." (Journal of the Institution of Mechanical Engineers. Vol 152, p.419)