This humiliating proof of the fallibility of my judgement has left me wary about the practised fluency with which candidates assure you of their love of children and the unflagging ingenuity of their creative play strategies. Even so, like many parents, I still assume that sins of omission will be the worst consequence in the event of a bad decision. Jessica Fowle's film added energetic malevolence to the list of anxieties that already swarm round working parents' heads.
Was it right to do so? I don't mean by this that there is anything wrong with a call to vigilance - the presence in this film of a woman who had hired a nanny without checking any of her references suggested that there are parents with a reckless confidence in their own emotional intuition. As one psychologist observed, some people research the purchase of a new washing machine with more care than they devote to the employment of a nanny. It is better, surely, to risk over-zealousness in one's scrutiny than to be as lackadaisical as that.
But did the awful video of nannies assaulting and abusing very small children represent a useful truth about nannies in general? Almost certainly not. And because film in which nannies genially go about their routine duties is not very interesting to look at, it is easy for two or three genuine horror stories to outweigh the countless cases of nannies who do their work conscientiously. Yes, they might sneak an illicit fag now and then, or even moan about their employers, but why should we expect of these workers (often underpaid and exploited) standards that would seem absurd with respect to any other kind of employment?
Of course, this isn't a matter where rationality is much to the fore - because the eddies of guilt (never quite admitted) and unease (never quite voiced) that swirl around the abandonment of one's children bring atavistic instincts into play. And it is only fair to add that Nannies from Hell properly reminded you that nannies can be victims of those primal rip-tides too. They can be particularly fierce when parents aren't entirely honest to themselves about their own motives and desires; the paradoxes were nicely summed up by the woman who had discovered satanic fantasies of harm scribbled in her nanny's diary: "I make huge personal sacrifices to ensure that he is looked after to the best of my ability," she said of her son, but these sacrifices didn't seem to include giving up the Merc and the top-flight legal career in order to apply her ability a little more directly.
I think the film was alert to such contradictions, and in its structure it offered a kind of common-sense sandwich made with very spicy bread; the middle part making the point that if you are uneasy enough to install secret cameras, you have almost certainly reached the point of no return anyway, while the opening and closing section offered grainy substantiation of your very worst fears - the dread that the clunk of the front-door closing might just serve as a starter's pistol for cruelty or neglect.
If this combination proved indigestible to any parents watching (the need for trust being difficult to reconcile with such vivid evidence of the rare occasions when it is betrayed), it was probably because the message was unpalatable, rather than this particular messenger.