Ar the risk of presenting yet another story of "bone headedness" ( I came to this thread late) some months ago I went through security at Humberside Airport en route to Europe. My case was subjected to an "in depth" check and when the security man found a battery operated alarm clock, he became very suspicious. I was then asked to set the alarm and prove that it worked.
The implication of what he was asking me to do obviously escaped him. If the "device" had been a timer for something more sinister then neither of us would have been here now.
I tried to point this out but his reply was that if he didn't hear the alarm going off (without the subsequent bang - I presume) then I would not be travelling.
Some months later, the local radio station disclosed that the high security fence around the airport was only partly competed because of lack of funds. The interview with the (I think) Airport Manager over this obvious lack of security only produced waffle.
Nuff said!