GIVEN that he's a devout Catholic, it's perhaps not surprising that Channel 4 boss Mark Thompson's favourite show on his own channel is a series in which Archbishop Rowan Williams pontificates on morality. But it's the morality of some of the channel's other programmes - Pornography: The Musical, Teen Big Brother and Sex Rules, as well as the attention-seeking stunts of Derren Brown and David Blaine - that has provoked rather more national comment.

Discussing anal sex on TV with the bearded and highly cerebral Mark Thompson is not unlike debating faith in the modern world with the Archbishop of Canterbury. Calm and urbane, Thompson is broadcasting aristocracy, fast-tracked through the BBC and tipped for future director-general, but he tends to eschew the world of TV glitz for family life in Oxford.

As he sips tea in his Channel 4 office - which he is giving up in favour of a democratic openplan workstation - he seems a most unlikely holder of the title "pornographer-in-chief " which was levelled at him over last night's documentary. In the programme, porn- film actors discussed in detail the indignities of their work, much of it anal sex, interspersed with songs.

"Pornography was a very tough watch but a thoughtful, serious documentary.

It was self-evidently a serious piece of work which would seriously disappoint people looking for cheap titillation," he says. Nor did he think scheduling such programming was in any way incompatible with being a person of religious convictions.

For one as "sheltered" as himself about such things, the information was shocking, but the most "disturbing" aspect was that most of the women interviewed seemed quite relaxed and happy with their work.

He's unrepentant about the controversy because, overall, Thompson claims, people are wrong to get excited about sex on Channel 4.

"We do our work against a very conservative backdrop of comment about television. The odd thing is, there's less programming of sexual content on Channel 4 now than there has been in recent years. We're doing far fewer series about sex; it's just that they've all appeared in October. What we have had is a lot of TV worth talking about, such as The Deal, Derren Brown and David Blaine."

But in the case of the last two, weren't people mainly talking about whether they were cheap, voyeuristic stunts to drive up the station's ratings? "Well, in the world of illusion they do do stunts for stunts' sake," he protests.

"There's no enormous ulterior meaning. Derren Brown is an illusionist and the word illusion should have suggested something about what was going on."

But the channel had suggested the bullets were live (though later claimed that a blank bullet also counted as live and could kill). Thompson is at his most Jesuitical here. "I don't think we ever said he was using real bullets.

Is Russian roulette tasteless?

Well, magicians saw people in half, which is deplorable behaviour and against the law if you do it for real. This captured the imagination, and we got very few complaints, compared to, say, the decision to move Countdown to 3.15pm."

One of Channel 4's most successful techniques to escape the "boring box" has been the use of reality TV. Starting with Big Brother, the genre has moved through Masters and Servants, Jamie's Kitchen and The Salon, to Wife Swap.

But even here Thompson feels prickly about critics who were quick to judge before evaluating the educational worth of such shows. "Critics were very sniffy about series one of Wife Swap. They came expecting it to be cynical and voyeuristic, but actually it's rather interesting and gives viewers perspectives about the way we live together, and what it's like looking after children. It's one of the documentary series of the year and deserves to win awards."

He concedes there is a danger of the channel becoming over- reliant on the reality genre. "I would say we've got by far the best record of innovating in this area. This year we've had wonderful shows, such as Operatunity and That'll Teach 'Em, but I do think Channel 4's schedule will be healthier when there's a stronger mixture of fiction, scripted drama and comedy. Coming up we've got Paul Abbott's Shameless and No Angels by Tony Garnett, about the NHS, and that's all about trying to build a body of drama that has things to say about contemporary Britain, but that people can bond to."

THE arrival of Kevin Lygo, plucked from Channel 5 to become director of programmes next week, is integral to building this new schedule. "I'm beginning a process of creative renewal at Channel 4, and part of that is taking programmes at the end of their lives, such as Brookside, Fifteen to One and Eurotrash and saying let's move on."

He's certainly an effective executioner. Since becoming chief executive 18 months ago, Thompson has already made his mark, cutting costs by half, slashing staff numbers from 1,100 to 850 and dismantling the costly FilmFour.

Channel 4 was back into the black last year, with a pre-tax profit of 16.5 million.

The fight for ratings is more important than ever - the channel saw its share of viewing dip to below 10 per cent for the first time since 1990, in the first six months of this year.

Channel 4's share was 9.5 per cent, compared with BBC2's 10.9 per cent, BBC1's 26 per cent and ITV's 23.8 per cent. And yet, in a week when ITV has been tearing itself apart and the BBC is under scrutiny as never before, Channel 4 still seems about the pleasantest place in broadcasting to be. How nice to be sipping tea and defending controversial programmes, rather than facing a vicious boardroom rout or a government review.

In fact, Thompson has plenty more to defend.

The next few months promise a drama documentary about 11 September told from the point of view of the hijackers, which American networks have refused to co-fund, and a workin-progress called Death Row: The Musical, featuring genuine prisoners awaiting execution.

He says he's not complacent, he just doesn't intend to get any safer. "I want to get a little bit braver, back to the sense of Channel 4 being the most talked about television. It's a small channel with a big voice, and although crucially it mustn't seem cynical or exploitative, this is an organisation which is 20 years old, and we want to start thinking like a channel which is two or three years old again. We're very lively and prepared to be cheeky and not to be too frightened of cartoons in the Daily Mail."

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