did-you-kno:

During WWII, England sent thousands of
Nazi POWs to stately homes where they
could eat, drink, play pool, and even keep
servants. They had no idea that all of the
rooms were bugged and many of their
fellow ‘prisoners’ were actually Germans
of Jewish origin who became spies for
the British after being forced out of their
homeland. The information gained was
so important that the government gave
them an unlimited budget. Source