I suppose we must accustom ourselves to the fact that some 30 years ago Britain was in the grip of a terrible paedo–geddon — even if, at the time, we did not quite know it. More shockingly still, it was not simply light entertainers who were fiddling about up and down the country, with their cunningly coded messages to children about having an ‘extra leg’ and sinister injunctions to restrain kangaroos.