It's dirty work, but someone's got to do it. In Fresno, California, Louis Theroux was hanging with his new friends, Kevin and Wiggle. They had asked him over to their place - you know, just your regular homey crystal meth den - for a barbecue, and Louis, keen to experience "the depths of the meth lifestyle", had accepted their kind invitation with some alacrity. The only problem was that it seemed no chargrilled burgers were forthcoming; there wasn't even a family-sized bag of Doritos to hand. Instead, poor old Louis was forced to stand in Kevin's yard late into the night - it was midnight, way past Louis's bedtime - hungry and probably a little bored, as Kevin and Wiggle kept disappearing for comfort breaks. Why did they do that so often? Louis, beady as ever, was suspicious. Could it be that his pals were busy getting high?
In the end, their manners and their inhibitions shot to pieces by their drug of choice, Kevin and Wiggle smoked some meth right there in front of our ace investigator's nose. This should have been a grim scene, seedy and sordid, but for some reason it reduced me to hysterical laughter.
The expression on Theroux's face! He looked exactly like one of those trendy, guitar-playing vicars, the kind that loves the sinner and hates the sin, but is also far too desperate to be liked to mention the sin. Only he was acting, of course, as he usually seems to be these days - for no one, least of all an experienced documentary-maker and weirdo hunter like him, can be this naive, surely? So beneath the vicar-style finish, as smoothly applied as varnish, I could also picture the ticker tape running through his mind. It said: "My God! This is going to be great for the film."
So, how was the film (BBC2, 9 August, 9pm; repeated Thursday 13 August, 11.20pm)? It was fine, the usual drill: go to America, where everything, from cosmetic surgery to drug addiction, is bigger and madder than it is over here; collect many interviews with the desperate and the crazy; edit; add sombre yet boyish voice-over. Kevin and Wiggle turned out to be just your regular criminal hoodies compared to most of the people Theroux hooked up with in Fresno, crystal meth capital of the world. At a needle exchange, he met Carl, who had been addicted for three decades. Carl took him home to meet his wife, Diane, who had occasionally been clean, only to find her resolve tested by the need to find the energy to vacuum-clean her sitting room.
“Some people drink coffee," she said, manically. "I do meth!" Louis's eyes widened, greedily.
Travelling the city with the police, he stumbled on an incident at a garage forecourt. A man had been fighting with a woman. Another woman arrived - the man's wife - who then explained to Louis that the first woman was her husband's sister, and that he was sleeping with her. "A strange parting moment to my experience of families destroyed by meth," intoned Louis in his voice-over. Strange is not the word I would have used.
All this stuff was predictably disgusting and scary, but still, I could have used a little more information. Such as: what exactly is crystal meth, and why is it so addictive? And why does it reduce your teeth to a medieval collection of brown stumps? In an aside, someone mentioned that it can be manufactured extremely cheaply at home, from cough medicine. I'd have liked to find out more about this. Will Buttercup Syrup do, or is something stronger required - for instance, Benylin?
The trouble is, I guess, that Theroux can't "interact" with facts the way he can with people. So it was back to California's largest rehab facility instead. How to describe this place? Well, imagine The Jeremy Kyle Show on a 24-hour loop, and you're about halfway there. Everyone cries and says sorry a lot - cue much rowdy applause - and then they go back out into the big, bad world and carry on pretty much as before.
It was only in this hellhole that I sniffed anything even approaching sincerity from Theroux. Holding hands with a couple of "reformed" addicts, he looked almost as embarrassed and sceptical as I felt.