A recent magazine poll - you know the kind of thing; readers' top 10 sex gods - revealed that women in the south of England regard Louis Theroux as Britain's most fanciable man. This perhaps says more about the sexual foibles of tennis-playing ladies of leisure than Louis himself - he is, after all, no Adonis: think gangly, little-boy-lost meets bespectacled trainspotting computer nerd and you get an idea of the image cultivated by a journalist who keeps knife-edged savvy tucked well underneath the trenchcoat.

His pedigree is exceedingly fine; he is the son of one Mr Paul Theroux, esteemed novelist and acclaimed travel writer. And yet nepotism has never been an element of his career trajectory. In fact, when Louis asked for dad's advice on how best to make it out there in the big, bad world, papa opined: ''Get away from me.''

Get away he did. And such has been the phenomenal success of his television documentaries, it's easy to believe son's star could one day outshine dad's.

Armed with no more than a bemused smile and a baggy jumper - and, of course, the ever-attendant entourage of video cameraman, soundman, director, stylists, runners, and gophers - Louis has made his name bringing into the mundane lives of British telly viewers the eccentricities of those humans whose lives are lived way, far, far beyond the pale.

And so in his first TV series, Weird Weekends, he led us with a stumble in his steps but a wink in his eye into the various worlds of hardcore pornographers, swinging couples - and even triples - extreme-right militants, fundamentalist, machine-gun-toting Christians, and stars-in-their-eyes humanoids who claim to have experienced close encounters with wee green men.

He could never have imagined entering this world of the weird and wonderful in his own childhood. He was born in Singapore to his scholarly American father and English mother, for a long time the head of arts and features for the BBC World Service, but young Louis was brought up in Dorset and then London at Westminster boarding school. He graduated from Oxford, where he read history.

When his parents divorced, Louis was already 23, but he admits the break-up of the family unit was still an incredible shock to him and his brother Marcel. Thankfully, it seems to have had little or no effect on his own irrepressible sense of mischief.

Tonight he brings his inimitable style to bear upon Miss Ann Widdecombe. The resulting documentary includes a review of her collection of teddy-bear motif crockery. We're also whisked off on an Arctic cruise, along with Anne's ma, Rita.

Not surprisingly, Miss Widdecombe is reputed to be less than overjoyed at how she comes across and it's surely a testament to Louis's persuasive talents he can still manage to get anyone at all to agree to face the camera. Then again, not many interviewers bring such a natural and humorous quality to a genre so overrun in recent years by a bullying, in-your-face style of confrontational journalism.

His expose of Jimmy Savile as a self-inflating windbag never seemed intentional: his style allows his subjects to single-handedly reveal their often less-than-palatable true selves. His sojourn in the world of Neil and Christine Hamilton could have made the odd-couple, who seem to thrive on flirting and double entendres, one of the great TV double acts, but for the fact that during filming they were accused, falsely as it turned out, of sexual assault. Compulsive television, all the same.

In the coming weeks we can look forward to close encounters with other British luminaries.

Louis Theroux asks the questions in When Louis Met Ann Widdecombe, BBC2, 9.00pm.