A rather desperate divinity teacher once asked my class to define faith. A clever clogs replied: "Believing in something you know can't possibly be true." "Wrong," snapped Dog Collar. Having watched BBC2's documentary Secret Swami (9pm, 17 June), I rather think that I was right after all. One of the richest supporters of the Indian guru Sai Baba - no less than Isaac Tigrett, co-founder of the Hard Rock Cafe - told his interviewer that he was perfectly willing to believe that Baba was simultaneously a) quite likely a paedophile and b) God incarnate.
Sai Baba does not look divine. He looks like a version of Diana Ross whose bumpy fall down the ugly tree has delivered her the worst hair day of her life. When he was a child, his parents found a cobra sleeping with him in his cot. They concluded that their son must have miraculous powers - a judgement he happily went along with when, aged 14, he declared himself God. By 1950, he had opened his first ashram. Now aged 77, he has the biggest draw of India's spiritual leaders, claiming 30 million followers in 165 countries. In a land of "god-men", he is the number-one brand, his face appearing on the fullest range of tat, from wristwatches to tea towels.
The reporter Tanya Datta - whose family presumably hails from the subcontinent - was careful not to make Baba's Indian supporters look like complete idiots. Producing necklaces and rings from thin air may seem small beer to us, but then we have watched Derren Brown. And there is no doubting Baba's miraculous ability to raise money to pump fresh water to remote villages in Andhra Pradesh and to build a new, free hospital designed by one of Prince Charles's favourite architects, Keith Critchlow (worryingly, given his proximity to the Crown, another devotee). Given that Baba's credo adds up to no more than "Peace and love, man" and "Could I touch you for a fiver to charity?", Indians could argue that old blubber-lips does more good than harm. But the nation's top guru-buster Basava Premanand, a man who can match most maharishis not only trick for trick but beard-whisker for beard-whisker, would disagree. He told Datta that India needs to rid herself of superstition before she will get anywhere.
But perhaps India is not where he should start. The documentary discovered that, as so often, the road to pseudo-enlightenment ran through North America. There, Datta interviewed Mark Roach who, after 25 years of Baba discipleship, finally got a personal audience with his guru and discovered it was far more personal than he wanted. "Why would God want to put his penis in your mouth?" Datta asked. "You've got me there," conceded Roach.
A particularly well-meaning but be-nighted American family had built a community devoted to Baba in Arkansas and in return was festooned with gifts, including the swami's old shirts. But in their case, their faith - strong though it was - did not exceed their love for their son Alaya, who claimed that Baba's powers of manipulation extended to the laying on of hands on teenage genitals. Distraught, they turned to the cult's international chairman Michael Goldstein, who promised to investigate but whose methodology was to open the case by asking Baba if the allegations were true and then to close it when he replied: "No, I am pure."
Despite the farcical credulity of Baba's western supporters, and the colourful ceremonies, the allegations of sexual assaults darkened the film. Baba is frail now. He came over so queer during one recent attempt to lay a golden egg via his mouth that his supporters must have feared he was going to do a Tommy Cooper on them. But by the end, the documentary had still managed to build up a fine head steam of outrage in this viewer. What I wanted was a cathartic confrontation with the mystic himself. Instead we had to make do with some secret filming of Goldstein, whose faith in Baba was surpassed only by his faith in his own abilities as a judge of character ("I'm a consummate professional"). An interview with a minister from the Indian government, which out of political expediency has long been in cahoots with Baba, was terminated when he began shouting: "Do you know who you are talking to?"
Datta held her own perfectly well. She is one of a chosen group of reporters trusted with presenting documentaries in the This World strand, which replaced Correspondent earlier this year. The camera lingered lovingly on her often enough to confirm that she was anything but an old man in a linen suit, which was the BBC hierarchy's complaint against the old show (although This World's second edition in January bravely bucked the trend by sending Michael Buerk back to Ethiopia). Recent editions have featured murder in Los Angeles and an exclusive interview with Mordechai Vanunu. Forthcoming is the child sex trade in Costa Rica. The same unit is responsible for BBC2's World Weddings, which most recently hymned a love affair between two HIV-positive Iranians. These programmes compare with Correspondent's slate in its last year: investigations into Yasser Arafat, the Indian dowry system, the West Bank and the spinning of the Private Jessica Lynch story.
Highly watchable though This World is proving, sceptics would say it shows the BBC dumbing down its foreign affairs agenda. Me, I have faith.
Andrew Billen is a staff writer on the Times