Between Silk and Cyanide (1998)

Serving as the cryptographer for Britain's Special Operations Executive, Marks supplied bespoke poem ciphers printed on silk to undercover agents parachuting behind enemy lines. His witty, harrowing memoir charts frantic mathematical duels against the Gestapo as he struggled to safeguard operatives from fatal radio deception. It is an extraordinary frontline espionage testament, conveying the agony and ingenuity of wartime codecraft with theatrical brilliance.