Second World War: The Secret Listeners by Sinclair McKay: review Ray Fautley was 12 when he built his first radio set and had worked for radio firms, including Marconi, since he was 14. When the man from Whitehall came calling, tipped off by one of Fautley's work colleagues, the 17-year-old was living at home. The civil servant told his worried parents that he wanted his son to do work of great national importance and recruited Fautley to the Y Service - Y for Wireless Intelligence or WI. Fautley became one of the war's "secret listeners." His instructions were to tune into bands 7 to 7.5 megacycles per second, write down any Morse signals he heard and send them in. Throughout the war he eavesdropped on the German secret service for two hours a night, five nights a week, and then did his day job with Mallard. Sinclair McKay follows his recent bestseller on the secret history of Bletchley Park with another "secret" from the war - the story of the Y Service, the men and women who monitored German Morse signals for clues to the military intentions of the Nazis. Y's listeners eavesdropped on the entire German war apparatus, every hour, every minute of the day. They sat with pencil, paper, a clunky radio set and listened to the monotony of Morse signals. The job required exemplary discipline and mental hardiness. They worked across the world, from Murmansk to Cairo, from Mombasa to Delhi and Hong Kong, and in Britain from the Orkneys to Dover. As well as accomplished linguists and highly intelligent Wrens, the Y service used an army of schoolboy radio hams who knew how to build their own wireless sets. Eventually there were about 1,500 teenagers like Fautley who were thrilled to spy on the Germans. Those who worked for the Y Service could start only when the enemy started work: and then they were required to work at dazzling speeds with minds concentrated like lasers; this was not a job for older people; even those in their mid-thirties were liable to burn out swiftly. Many successes can be attributed to the Y service. Rommel had reason to curse them since it was the listeners who played a decisive role in the turning of the desert war: Y intercepts gave Montgomery an outline of Rommel's attack plans. The Russians were supplied with vital information about German tanks that enabled them to win the 1943 Battle of Kursk. Y decrypts were crucial in the Battle of the Atlantic and in Normandy after D-Day. As McKay argues in this well-told story, the Y Service has been "sadly and curiously" uncelebrated. Yet were it not for all those encoded messages relayed with such care, the codebreakers of Bletchley would have had little to go on. All the boffins, all the brave Wrens sailing to new listening posts, the agents in the field, the thousands of women permanently damaging their hearing for the sake of doing their duty - it was their efforts that made the revolutionary leaps of Bletchley possible. They should be commemorated properly as having played their parts in one of the greatest achievements of the 20th century, he says. And he has done them proud. The Secret Listeners by Sinclair McKay is available from Telegraph Books at £18