More family memorabilia.   During the war every RAF airman who might fly over enemy territory was issued with guidelines of precautions to be taken in the event of being captured.  They were advised of ways in which an enemy could get information by simulating professional, technical or friendly interest or by agents who were seemingly sympathetic like hospital nurses or even people impersonating prisoners.   Inevitably there would be hidden microphones.  Say nothing and go on saying it.  Before flying pockets had to be emptied as even a clothing label or old tram ticket or bill could provide information and of course envelopes and diaries would give invaluable information.  The leaflet finishes by telling the person not to be downhearted if captured and giving advice on the rights of a Prisoner of War. 
Similar advice will be commonplace today.  Two army officer relatives have recently been deployed and although they have not been prisoners they had to be careful depending upon their posting, when talking to their partners by phone by having to use code for places or even in naming their own relatives at home.