In the sixties everyone in certain trades had to watch several "security" films every year and receive a lecture from the P&SS people. The P&SS people got very upset when everyone in the room had seen the films 20 or 30 times, knew the film scripts off by heart and enjoyed speaking along with the actors on the screen; other tactics to enliven these events included treating the film as a pantomime, complete with booing the "baddies", cheering the "heros" along with sharp intakes of breath and calls of "he's behind you" at appropriate moments.
The main lesson for everyone was that familiarity breeds contempt when handling highly sensitive material. Examples of this were senior officers leaving classified material in their car while they went shopping or leaving their briefcase on the train.