The Weekend's Viewing: The South Bank Show, Sun, Sky Arts 1Sebastian Bergman, Sat, BBC4

There are only a handful of TV institutions that have remained essentially unchanged for more than 30 years and in the case of The South Bank Show at least two of the hallmarks are aural.

There's Andrew Lloyd Webber's jaunty theme tune, traditionally played out over a scudding montage of cultural hieroglyphs, and there are the eminently imitable tones of Melvyn Bragg, the voice that launched a thousand impersonations. Both are comfortingly just as they always were after the programme's transfer from ITV to Sky Arts 1. And last night's opening show began with another reassuring touch for the strand's long-running fans – one of those uncheckably vague superlatives that traditionally underwrite the choice of topic. Nicholas Hytner, subject of last night's profile, is, we learned, "thought by some to be the best theatre director in the world right now". Who exactly "some" are doesn't need to be specified, of course; the point is to reassure us that quality control isn't asleep on the job.

The resulting head-to-head was a curious mixture of interview and conversation. At times, Hytner answered with a slightly pre-prepared gloss, as if he was a senior public servant who'd rehearsed the tricky ones with his advisers. At other times, he relaxed a bit and just let his enthusiasm for the theatre flow. The conversation bits were better than the interview bits, and even better than those was the documentary access to Hytner reading notes to the cast of One Man, Two Guvnors on Broadway, applying in practice the talents he'd earlier sketched out in theory. Learning how to direct, he'd implied to Bragg earlier, was an apprenticeship in humility: "Anybody can read, ideas are two a penny... it's the ability to cajole other people into realising your ideas that you develop."

It never really probed too deep into the question of what a national theatre should be. Hytner himself eventually summed it up as "an essential weapon in the campaign to know ourselves better", but there wasn't a lot about what happens when the weapon backfires. Richard Bean, for example, contributed to the programme because of his part in One Man, Two Guvnors but there was no mention of the turbulent response to his earlier play England People Very Nice, which grasped the nettle of immigration and racist caricature (and, it could be argued, epitomised the duty of a national theatre to risk antagonising its audiences in the course of depicting them). And the contributions of really thoughtful writers and actors, such as Alan Bennett and Simon Russell Beale, were restricted to the kind of good wishes you might stick in a birthday video.

But it was interesting to see how bluntly practical Hytner's tweaks were after an early Broadway preview for One Man, Two Guvnors, in some cases diagnosing a problem and putting it right in one sentence. "I think what's happening is to play stupid, you're playing slow," he told one actress, "but I think stupid and quick are not necessarily mutually exclusive." It's good to have the old show back.

In a different context there is also an association between slow and clever, thrillers being particularly prone to dragging things out if they want to appear cerebral and philosophically deep. Sebastian Bergman also comes with those currently modish accessories, a Swedish soundtrack and subtitles, but if you strip those away it should be pretty obvious that this is a routine detective drama, and no substitute at all for The Bridge. It's Cråcker essentially, with Bergman as a rumpled, womanising profiler who is helping the police with the investigation into the gruesome murder of a schoolboy. "Helping" means letting them waste a day or two on a fruitless line of inquiry and then casually announcing that "the boy next door is innocent... it's obvious". Quite useful to wean yourself off an addiction to Scandidrama, but not strongly recommended for anything else.