British intelligence undertook an audacious operation to listen in on the private conversations of 10,000 German prisoners of war without their ever knowing they were being overheard. The prisoners' unguarded reminiscences and unintentional confessions have only just come to light, and prove how closely the German army were involved in the atrocities of the Holocaust. British intelligence requisitioned three stately homes for this epic task, and converted each into an elaborate trap. The 100,000 hours of conversation they captured provide...