Behind the celebrated code-breaking at Bletchley Park lies another secret. Before the German war machine's messages could be decoded - turning the course of the war in a campaign like the Desert War - thousands more young men and women had to locate and monitor endless streams of radio traffic around the clock, and transcribe its Morse code with a speed few have ever managed since. They were part of the "Y"- (for "Wireless") Service: the Listening Service - an organisation just as secret as Bletchley Park during the war, but nowadays still little-known and unrecognised. Without it, however, the Allies would have known nothing of the enemy's military intentions. Now, in the follow-up to his Sunday Times-bestselling The Secret Life of Bletchley Park, through dozens of interviews with surviving veterans, Sinclair McKay chronicles the history and achievements of this remarkable group of people. Whereas Bletchley Park was a claustrophobically close community crammed into a single Buckinghamshire mansion, the Listening Service went wherever the war went - which was all over the world. Its listeners might be posted to bustling Cairo to listen in to Rommel's Eighth Army, or Casablanca in Morocco, or Karachi for the Burma campaign, or in one case even the idyllic Cocos Islands in the Indian Ocean to monitor Japan - or they might be sent to congenial Scarborough or Douglas in the Isle of Man to listen in to German submarines. To men and women often hardly out of school such exotic postings were life-changing adventures - even the journey out could be an epic voyage of troopships, flying boats and Indian railways - and the challenges not merely arduous night shifts of 12 hours of dizzying concentration, but heat so intense the perspiration ran into your shoes, or snakes in the filing cabinets. In all of them it bred self-reliance and broad horizons rare to their generation, while many found lifelong romance in their far-flung corner of the world. Now the hidden story of the Y-Service and its vital contribution to the war effort can be told at last.