Actually, when I say 100,000, that's just the figure that an organisation, Faith Matters, put on the trend last week. It follows a separate report by the US-based Pew Forum, which said that there are, in fact, 2.9 million Muslims in Britain, a hefty increase from the 1.6 million in the 2001 census. But we'll have to wait until the entire Pew Forum report is published to work out whether they're attributing this to conversions or to undercounting at the last census, which would be my own instinctive assumption. As for the Faith Matters report, an analysis by Steve Tomkins on The Guardian website suggests that their figures aren't altogether robust, being based on an extrapolation from Scottish figures in the last census to the whole of Britain, and on a phone round of London mosques, in which 8 percent of them responded.

Nonetheless, there plainly is something going on here, though, as an interesting report on Radio 4 made clear, a significant number of the new Muslims, at least in London, are in fact West Indian youths, for whom Islam offers greater discipline and certainty than the Pentecostalism of their parents.

Where the Faith Matters report is convincing is in its interviews with real converts, of whom Lauren Booth seems typical, though rather older than the average, which is aged 27, female, white and fed up with the mores of contemporary Brits. The interviewees identified alcohol and drunkenness, a "lack of morality and sexual permissiveness" and "unrestrained consumerism" as aspects of British society for which Islam was a remedy. Or as Ms Booth put it, after conversion to Islam, "I have glimpsed the great lie that is the facade of our modern lives; that materialism, consumerism, sex and drugs will give us lasting happiness."

Well, bully for her. I can't help feeling a batsqueak of unease, though, at this sweeping condemnation. In the wake of the troubling cases of men in the Midlands - of "Pakistani heritage" as Jack Straw delicately put it - preying on young white girls, there seems a worrying association between the attribution of a superior class of social morality to Muslims and the contempt shown by the convicted predators towards non-Muslim girls. It's a phenomenon that the commentator Yasmin Alibhai Brown identified in The Independent as a problem specifically to do with a particular kind of mindset among a particular class of Muslim men, the sort who perpetrate honour killings.

But even if you concede that any Saturday night city centre in Britain will underpin the notion of a culture of slapperdom and alcoholism, you have to ask why the new Muslims have to go so far out of their way for a remedy. Actually, in my experience, many girls who convert to Islam do so because their boyfriends/ future husbands are Muslims - see Jemima Khan - and the girls' religious identity is simply less robust than theirs where it exists at all. But if hedonism/mindless materialism/ sexual promiscuity/alcoholism is the problem for which Islam is the solution, you wonder why they can't look for it closer to home.

In other words, if you want a worldview which makes all the above redundant, Christianity, the local brand, does offer an alternative. (Indeed, in the case of Ms Booth, her mother's Judaism would do so too.) Christianity has, in St Paul, rather a high estimation of the human body and our duties towards it - he called the body the temple of the Holy Spirit, if you remember, which makes mindless sexual excess and gluttony something akin to blasphemy. As for fornication and adultery, they are, as far as St Paul goes, conduct unbecoming to those made in God's image.

So why is it that the young folk revolted by contemporary excess don't simply make for the local CofE, or Catholic church, and rediscover the religion of their grandmothers, rather than getting their spirituality via Islam? It is, I think, something to do with the real malaise of contemporary Britain which I wrote about in a little essay in The Spectator concerning the film Eat, Pray, Love. It is the notion that what exists abroad, or what is foreign to your own background, is somehow superior to what you've grown up with, what's under your nose. In the case of EPL, the heroine finds her spiritual identity in Buddhism. It would have been a good deal more interesting if she could have discovered it in her local Episcopalian church.

It may be that the British young don't embrace Christianity because they simply don't encounter it, at least not through the kind of religious education-as-anthropology they get in state school, which is about as opposite as it is possible to be from the Sunday School teaching which their grandmothers would have got. Actually, the death of the Sunday School pretty well marked the end of any practical instruction in Christianity for most children. No wonder they're susceptible to the certainties of Islam, when they encounter it.

But the notion that Islam is the one bulwark against mindless excess does deserve a polite, Anglican rebuke. Or indeed, that improbable thing: a counterblast from the Archbishop of Canterbury. Rowan Williams can do it, you know. In one recent lecture he declared:

"We need to be set free to be what we were created to be - and we were created to be something in particular. We were created to be sons and daughters of the heavenly Father. So part of the New Testament claim is actually that there's something about human beings which is true universally; an orientation, a magnetic 'drawing-towards' the source of all things, and a capacity to relate to the source of all things, not simply as someone who obeys or thinks, but as someone who is related intimately and intensely; like a child to a father. That's what human beings are made for."

That seems to me like a pretty good alternative to mindless materialism and, come to that, a pretty good alternative to Islam. But coming from the CofE, it's something young Brits are almost conditioned not to hear.

END