The story of Bletchley Park's codebreaking operations in the Second World War is now well known, but its counterparts in the First World War – Room 40 & MI1(b) – remain in the shadows, despite their involvement in and influence on most of the major events of that war. From first Battle of the Marne, the shelling of Scarborough, the Battles of Jutland and the Somme in 1916, the first 'Battle of Britain', the 'Zimmermann Telegram', to the Battles of 1918 on the Western Front and the German naval mutiny, this cast of characters – several of them as eccentric as anyone from Bletchley Park in the Second World War – secretly guided the outcome of the 'Great War' from within the smoky confines of a single room. Using hundreds of intercepted and decrypted German military, naval and diplomatic messages, bestselling author Paul Gannon reveals the fascinating story of British codebreaking operations. And by drawing on many newly discovered archival documents which challenge misleading stories about Room 40 & MI1(b), he reveals a sophisticated machine in operation. AUTHOR: Paul Gannon is a journalist and writer who specialises in information and communications technology. His first book, Trojan Horses and National Champions, was awarded the IT Book of the Year in 1997. More recently, he has written the bestselling Colossus: Bletchley Park's Greatest Secret for Atlantic Books. 20 b/w illustrations