Made me think of that PBS documentary, 'Bugging Hitler's Soldiers'

In some sites around Britain, German officer POW's had their rooms bugged, which the POW's apparently were unaware of. Even trees and planter beds outside the buildings were bugged (as was depicted in this film). This allowed for copious amounts of detailed military data to be compiled by the British intelligence folks who did the eavesdropping. Talk about "loose lips"! See the documentary online:

http://www.pbs.org/wnet/secrets/episodes/bugging-hitler%E2%80%99s-sold iers-watch-the-full-episode/947/