The author, at twenty-three, became head of codes at the Signals branch of SOE (Special Operations Executive) and changed the way the British ran codes. When he arrived, they were using poems a basis for their character transposition, a process that was open to typos and was easily cracked if a few key words of the poem were deciphered and the phrase was well known. Regarding the typos, Marks impressed his superiors by insisting that indecipherable messages would be cracked at SOE, without asking the agent in the field to take the risk of resending a new message. Hating the poem codes in general, he doggedly pushed against the bureaucracy who balked at all change, arguing for a system he called WOKs, for Worked Out Keys, and inventing what he called LOPs, or Letter-based One-time Pads, both of which could be used once and then destroyed. He also innovated the printing of codes onto the titular silks, which are easier to hide than paper.
From page one, Marks jumps right into the story, bringing only the bare minimum of relevant biographical details, which is refreshing. He’s a smart and funny narrator with a flair for puns and self-deprecating humor, which he manages to maintain over 600 pages without it becoming tiresome. But he knows how to tell a story, too. The main drama in the book is the Holland section, which Marks suspects has been compromised very early on due to their too-perfect coding. He cannot convince his obdurate employers, and he sees with chagrin agent after agent, and secret after secret, fall into the hands of the Germans who are maintaining the charade of communication with SOE. Finally, he takes matters into his own hands, and even if, as in fiction, there’s no dramatic act of closure, the way in which he works without the consent of his superiors to set a trap for the Germans is quite admirable. It’s a very well done memoir, and even if much of the coding went over my head, I found that as a record of how the British intelligence service operated in WWII, it’s hugely instructive as well as entertaining.