PBS America: Spying On Hitler’s Army: Monday 5 September at 7.35pm

The Second World War would see enormous numbers of captured combatants on both sides confined to POW camps. Officers fared better than ordinary soldiers – some higher-ranking Germans in British custody were even lucky enough to end up incarcerated in former stately homes.

However, unbeknown to these particular captives, their conversations were being monitored through hidden microphones, and they let slip far more than just name, rank and serial number. With their guard down, their inner thoughts were carefully recorded, as was their complicity in crimes against humanity.

From this clandestine campaign emerged military secrets that would help the Allies gain victory. Over 70 years on, historic transcripts reveal the startling extent of this information gleaned from eavesdropping on the enemy.