Before reading [writing] this history I have not had the unpleasant task of reading voluminous records and scanning innumerable documents. We have never been enthusiastic keepers of diaries and log books and have habitually destroyed records when their period of utility was over and it is the merest chance that has preserved a few documents of interest; hardly any of these are dated. Since March 1943 the Weekly Report to the Director provides a valuable record of our activities but it is naturally this more recent period which human memory most easily recalls and it is the lack of documentary evidence about early days which is the most serious. A very large portion of this history is simply an effort of memory confirmed by referring to other members of the Section. I joined the Section myself in October 1941 and have fairly clear personal recollections from that time; for the early history I am indebted primarily to Turing, the first head of Hut 8, and most of the early information is based on conversations I have had with him. I also owe a considerable debt of gratitude to Mr. Birch who lent me the surviving 1939-1940 Naval Section documents which yielded several valuable pieces of information and afforded an interesting opportunity of seeing Hut 8 as others saw us. Many past members of the Section and many people from elsewhere in B.P. have been kind enough to answer questions and special mention must be made of the contribution of Ashcroft who wrote the long chapter on Short Signals which I have incorporated unchanged into the book: Short Signals were for a long time a specialized research subject on which Ashcroft was the expert and his description of the work involved is far more accurate and exhaustive than mine could ever be.
With the exception of Turing, whose position as founder of the Section is a very special one, I have adopted the policy of not mentioning individuals by name. Attributing this or that accomplishment to an individual would be an invidious process contrary to the traditional attitude of the Section towards its work and it would inevitably give a misleading impression of the relative contributions of the different members of the Section.
It is impossible to write a truly objective history of a Section which has been ones principal interest in life for the last 3½ years and so this book is written on a comparatively personal note - mostly in the first person plural with occasionally a purely personal recollection or opinion included: to the best of my ability I have only introduced by "we" opinions with which the Section as a whole would have agreed. We have always prided ourselves on not trying to conceal our failures and on admitting where we might have done better and I have attempted to avoid any tendency to "whitewash" our efforts for the benefit of posterity.