Louis Theroux: A Place for Paedophiles, Sunday 9pm, BBC2

After all those years spent squirming in the spare rooms of Sir Jimmy Savile, Paul Daniels and the Hamiltons, the BBC evidently feels poor Louis Theroux deserved a bit of a break.

For the latest instalment in his gradual reinvention as a Proper Serious Journalist - less eyebrow arching, same interview technique - he was packed off for a week’s holiday on the sunny West Coast of America to spend time with 800 or so of America’s most notorious sex offenders.

Coalinga, California is the site of a controversial mental hospital for paedophiles, where 800 offenders are locked up indefinitely despite already serving their prison sentences. Eager to quench the placard-waving, “cut off their balls with a rusty penknife”-bellowing public’s demand to keep these people off the streets, the authorities have exploited a legal loophole and reclassified ex-prisoners as mentally ill – in effect giving themselves carte blanche to incarcerate them indefinitely.

Some of the lead-up to the show was particularly knee jerk. Under the headline "Day I Met the Paedos in Paradise" The Sun described Coalinga as a place where “vile sex beasts have karaoke nights, put on plays, and on their birthday are thrown a party with cake, ice-cream and gifts”. Well, it’s all true, but that’s not exactly the full story.

In its entire history, only 13 inmates at Coalinga have been released back into the community. Part of the reason for this is that there’s not actually any evidence, despite Coalinga’s extensive series of "phallametric" tests, stints on the lie detector and daily group therapy, that paedophilia is actually something that can be “cured”. As a result, the hospital has become little more than a huge, expensive holding ground.

A significant minority of the inmates even refuse to cooperate with therapy, preferring instead to try to make their escape by means of a legal challenge. One inmate describes the whole process as “locking people up just in case they do anything”, and other scenes, such as the forced, half-hearted apology after a stand off between a therapist and a petulant Coalinga patient suggests the only thing these men are learning is how to play the game.

It was a brave documentary, unafraid to portray sex-offenders as the deeply flawed human beings rather than sub-human bogeymen as is often (perhaps rather conveniently) the case. One thing’s for sure – splashing out £137,000 a head each year from the public purse to keep them locked up on a course of ineffectual rehabilitation doesn’t seem to be the solution.