The World War II codebreaking station at Bletchley is well known and its activities documented in detail. Its decryption capabilities were vital to the war effort, significantly aiding Allied victory. But where did the messages being deciphered come from in the first place?

This is the extraordinary untold story of the Y-Service, a secret even more closely guarded than Bletchley Park. The Y-Service was the code for the chain of wireless intercept stations around Britain and all over the world. Hundreds of wireless operators, many of them who were civilians, listened to German, Italian and Japanese radio networks and meticulously logged everything they heard. Some messages were then used tactically but most were sent on to Station X - Bletchley Park - where they were deciphered, translated and consolidated to build a comprehensive overview of the enemy's movements and intentions.

Peter Hore delves into the fascinating history of the Y-service, with particular reference to the girls of the Women's Royal Naval Service: Wrens who escaped from Singapore to Colombo as the war raged, only to be torpedoed in the Atlantic on their way back to Britain; the woman who had a devastatingly true premonition that disaster would strike on her way to Gibraltar; the Australian who went from being captain of the English Women's Cricket team to a WWII Wren to the head of Abbotleigh girls school in Sydney; how the Y-service helped to hunt the German battleship Bismarck in the North Atlantic, and how it helped to torpedo a Japanese cruiser in the Indian Ocean. Together, these incredible stories build a picture of World War II as it has never been viewed before.