A number of journalists have already had some fun with Mysteries with Carol Vorderman - mostly to do with the eerie ubiquity of a young woman who was once known only for her powers of mental arithmetic. Is some kind of bilocation involved? Is she a real person at all? Is that sci-fi name an acronym for some secret project in artificial intelligence?

Today - as they like to say - we can exclusively reveal that there is no enigma at all. The reason you cannot turn on your television set without seeing her is not because she is cheap - as she richly suggested in the Radio Times - but because she researches well (television talk for asking people whether they like her), and because there is zero career-risk involved in hiring her. Similar reasons account for the fact that whenever you can't see Carol Vorderman it is because Carol Smillie is standing in the way. I am told that Carol S recently worked on four different BBC programmes in a single day, which gives you a measure of the profound herd instinct that moves some television executives.

No great mystery about the presenter, then, and not much mystery about the programme, which is yet another attempt to feed the credulity of the viewing public. Why are they increasingly credulous? In part because of programmes like these - a kind of fungal growth which creates its own desired ecology in the human mind. The titles for this programme are tacky, the music is tacky, the reconstructions and visual style are tacky, but what is most tacky of all is the cosmetic powdering of inquiry with which it tries to conceal the unsightly gleam of calculation. "Mysteries are so good for business", as a nephew of Glenn Miller's said, after an item about his famous uncle's disappearance. This remark returned to mind after a film report on the use of dolphins as a therapeutic tool in helping disabled children: "Whether dolphin therapy really works simply because dolphins are nice creatures, or for some more complex reasons, is actually irrelevant to those families whose lives have been fundamentally changed by the experience," said Vorderman. But it may not be irrelevant for a poor family wondering whether to scrape together the $2,000 a week it costs for the treatment, and it should not be irrelevant to a public service broadcaster. The word "believe" tolled through this item like a bell: "the family believe" the treatment has helped their child; "some people believe they might be getting close to an answer" (the introduction to a "researcher", Horace Dobbs, who apparently "believes that dolphins have inexplicable powers" - in other words, that there is no explanation). Finally, "not everyone believes that dolphins have special powers" (the cue for a swift, face-saving explanation of the placebo effect). This casual redundancy blurred the distinction between beliefs founded on evidence and beliefs which are just wishes in disguise - but then, if too many of the audience understood that distinction, who would watch gimcrack entertainments like this?

Last week, Peter Taylor's fascinating series about the IRA turned up what looked like a real scoop in revelations of British hints that they were looking for a way out of the province. This week, more troublingly, it tackled the bloody war between the SAS and the IRA without once mentioning the words "shoot to kill". I have no sympathy for men who think that when they lie in hiding to kill without warning it is a heroic act - but that when the same thing is done to them it becomes a brutal atrocity. But the fact is that the killing of IRA gunmen in this period was a counter- productive strategy. Every dead man was a recruiting sergeant. The way in which Taylor tiptoed round the subject - he talked of the "secret war" and "fire ... being met with fire" - raised for the very first time an anxiety about off-screen pressure. Had Sir John Hermon made it a condition of his participation that the name Stalker and that controversial epithet were not spoken aloud in his presence?