The announcement that several thousand Mars bars had somehow been filled with rat poison would, in any normal town, have driven sales through the floor. Not here.
Kids were buying armfuls of the stodgy buggers,hoping to get one with that elusive blue biro cross that "proved" it had been injected with poison. Rumour had it that shopkeepers began to randomly mark Mars bars to sate the endless thirst for Work, Rest, and Death.
This led to a bizarre forms of playground bullying ever seen; a child would be forced by pogrom to consume a "tainted" Mars bar, after which he or she would be detained to allow the court to "observe the effects". Generally this would involve bad play-acting by the accused in a misguided attempt to make the court feel first guilty, then panicked, ideally summoning a teacher. Needless to say, this was wishful thinking, and the victim was "buried at sea" by hurling them bodily down a hill.
Nowadays we would be eating poisoned chocolate so we could sue for compensation. In 1986, we simply didn't have an excuse that good.