As is always the case, my wife Sarah has been absolutely invaluable, and no thanks could ever be sufficient in view of her support and assistance. I am also grateful to my dear friend Mrs Nora Relingh for valuable information about the Resistance in occupied Europe. In the Imperial War Museum’s Department of Documents I have put Emma Golding to a good deal of trouble, and I much appreciate her efforts. I also thank Rod Bailey, an authority on SOE, for advice. Eileen Simon, of the Veterans’ History Project at the Library of Congress in Washington DC, has been extremely helpful, as she has on previous occasions. The VHP, set up comparatively recently, is becoming widely known as an invaluable source for historians, and I feel privileged to have had access to it. I have received – as I always do – extremely helpful guidance from Ruth Binney and from Neil Baber. I would also like to acknowledge the help of Ame Verso, Emily Pitcher, Tracey Woodward, Steve Newman and Debbie Jackson. Finally, I wish to thank the many heroes and heroines of the codebreakers’ war who gave permission for their remarkable stories to be repeated here. Any errors are, of course, mine alone.