Room No. 40

In the corridors of the British Admiralty, where the fiercest intelligence battles took place in the shadows, Room (40) was home to brilliant minds who carried not weapons, but more dangerous tools: knowledge, analysis, and breaking impossible codes. There, an elite group of thinkers—scientists, lawyers, publishers, and even actors—met with one goal: to decipher the German code and reveal the enemy's secrets before it was too late. At the forefront of these was Reginald "Blinker" Hall, the man described by American intelligence as "the only genius developed by the war." Under his leadership, the team was able to crack the most complex codes, most notably the Zimmermann Telegram, which was the spark that pushed the United States into World War I and tipped the global balance of power. But this story didn't begin suddenly. It goes back years of covert work, from Welsh physicist Ted Palmer, who joined the force on a cold morning in 1914; to Nigel de Grey, the book editor who dabbled in cracking ciphers for fun; and to Dillwyn Knox, the papyrologist who accomplished his greatest work in the bathtub of his office! In these pages, you'll discover how the war of minds can be more powerful than the war of armies, and how the secret of the code was the greatest triumph in the history of modern intelligence.