Depending on the subject-matter, his mild yet dogged approach can yield some interesting results. But this big-screen documentary on Scientology — directed by John Dower, not one of Theroux's regular collaborators — is far from his finest hour. The immediate problem is that none of the current big cheeses in the movement are prepared to give Theroux the time of day. That leaves him relying on ex-believers with axes to grind, in particular former chief executive Mark Rathbun, a burly guy in his late fifties who you wouldn't want to get on the wrong side of.

Louis Theroux is known for tackling subjects like Scientology with his immersive journalism.

Driving round LA, Theroux lends a willing ear to Rathbun's tales of Scientology's toxic inner circle, with Rathbun himself emerging as a bully second only to church leader David Miscavige. It's hard not to be fascinated by the sheer weirdness of what seems closer to a deranged scheme than a religion in the conventional sense. But much of this material has been canvassed elsewhere — notably in Alex Gibney's recent documentary Going Clear — and major revelations are few.

Other scenes involve the staging of re-enactments of Rathbun's stories: various actors audition for the role of Miscavige, with Rathbun passing judgement on their resemblance to the real thing. This device is lifted from Joshua Oppenheimer's widely admired The Act of Killing, where those involved in Indonesia's anti-Communist purges were called on to re-enact their crimes. But the stakes here are considerably lower, and Dower and Theroux can't hope to match the disturbing power of their model.

The rest is padding, including the expected scenes where irate officials order the crew to stop filming and Theroux fights back with his usual earnest pretence of good faith. A special shout-out to American actor Paz de la Huerta (Boardwalk Empire) who shows up unexpectedly near Rathbun's pool, leading Theroux to ponder whether she might be the bait in a "honey trap". Whatever the truth of this, it's good to see her keeping busy during lulls in her acting career.