When I began the research for this series and read about all the colorful personalities that made up Room 40, I knew I couldn’t let THE CODEBREAKERS end without highlighting two of the people who most intrigued me—the Russian who fled the Bolsheviks and joined the cryptographers under Admiral Hall, and the unnamed photography expert who kept DID in a supply of falsified photographs to use against the enemy. Both of these characters have their basis in fact. But, of course, I fictionalized as well.

The real Russian cryptographer was Ernst Fetterlein, who was an Admiral-General in the Imperial Navy and head of Russia’s cryptography department, working under the name of Popov (because of the German sound of his actual last name). While he inspired the character of Zivon, I didn’t want to use this historical figure entirely, since he was a decade older than I wanted and already had a family. Instead, I used him as Zivon’s mentor, borrowed some of his stories—like the scene at the bank and the ruby ring he valued above all—and then made a hero of my own. I enjoyed creating a character with his own unique traits and imagining what it must have been like for a man to go from being the well-respected top of his department in Russia to a suspicious nobody among his English counterparts.

Lily’s character is largely fictional. I could find a few mentions of the work done by these staff photographers but not information on the actual people—which meant I was free to make it all up! It was fun (and a bit intimidating) to learn about early cameras and photography and, most of all, to imagine the world through the eyes of someone who sees it best through a camera lens. The photograph used to spur on the mutiny at the end of the war is a true story, which I learned about in Blinker Hall, Spymaster by David Ramsay. The massive bombing in London in May 1918 was factual (though not, so far as we know, a result of false information leaked to the Germans) and is referred to by historians as the first real blitz. All other specific occurrences of photos used for the war effort were my imagination.