The 1941 film A-tish-oo showed masks being used to prevent the spread of disease Credit: BFI A few nights ago, a couple of hours after lights-out time, I had to reassure my traumatised children that they weren’t about to be abducted by a pervert or dismembered in an industrial accident. The ideas had been planted that afternoon. We’d watched two short films together produced by the government’s now-defunct Central Office of Information: Never Go With Strangers and Building Sites Bite. Both were originally screened in British classrooms in the Seventies, and I was keen to see if they s...