We did something like this in about Y8 I think in some safety day on a trip at school. A policeman was talking to a group of us about drugs or something and he pretended he'd just received a phone call and had to leave us for a minute. When he'd gone this stranger came up to us pretending to be a staff member at this place asking if one of us could help him carry some bottles of water from his van back into the building. None of us thought anything strange of this and one of the group began walking off before the policeman came back and was like 'what are you doing about to walk off with a stranger?'...it was really cleverly done but pretty scary. It all hit us after that how easy it would be to be tricked into something, and that's stayed with me forever (even if it doesn't really apply to me anymore)
