It has been sobering this past week watching some of my "woollier" colleagues (in Vicki Woods's self-designation) gradually awake to the realisation that the real suicide bomb is "multiculturalism". Its remorseless tick-tock, suddenly louder than the ethnic drumming at an anti-globalisation demo, drove poor old Boris Johnson into rampaging around this page last Thursday like some demented late-night karaoke one-man Fiddler on the Roof, stamping his feet and bellowing, "Tradition! Tradition!" Boris's plea for more Britishness was heartfelt and valiant, but I'm not sure I'd bet on it. The London bombers were, to the naked eye, assimilated - they ate fish 'n' chips, played cricket, sported appalling leisurewear. They'd adopted so many trees we couldn't see they lacked the big overarching forest - the essence of identity, of allegiance. As I've said before, you can't assimilate with a nullity - which is what multiculturalism is.

So, if Islamist extremism is the genie you're trying to put back in the bottle, it doesn't help to have smashed the bottle. As the death of the Eurofanatic Ted Heath reminds us, in modern Britain even a "conservative" prime minister thinks nothing of obliterating ancient counties and imposing on the populace fantasy jurisdictions - "Avon", "Clwyd" and (my personal favourite in its evocative neo-Stalinism) "Central Region" - and an alien regulatory regime imported from the failed polities of Europe. The 7/7 murderers are described as "Yorkshiremen", but, of course, there is no Yorkshire: Ted abolished that, too.

Sir Edward's successor, Mr Blair, said on the day of the bombing that terrorists would not be allowed to "change our country or our way of life". Of course not. That's his job - from hunting to Europeanisation. Could you reliably say what aspects of "our way of life" Britain's ruling class, whether pseudo-Labour like Mr Blair or pseudo-Conservative like Sir Ted, wish to preserve? The Notting Hill Carnival? Not enough, alas.

Consider the Bishop of Lichfield, who at Evensong, on the night of the bombings, was at pains to assure his congregants: "Just as the IRA has nothing to do with Christianity, so this kind of terror has nothing to do with any of the world faiths." It's not so much the explicit fatuousness of the assertion so much as the broader message it conveys: we're the defeatist wimps; bomb us and we'll apologise to you. That's why in Britain the Anglican Church is in a death-spiral and Islam is the fastest-growing religion. There's no market for a faith that has no faith in itself. And as the Church goes so goes the state: why introduce identity cards for a nation with no identity?

It was the Prime Minister's wife, you'll recall, who last year won a famous court victory for Shabina Begum, as a result of which schools across the land must now permit students to wear the full "jilbab" - ie, Muslim garb that covers the entire body except the eyes and hands. Ms Booth hailed this as "a victory for all Muslims who wish to preserve their identity and values despite prejudice and bigotry". It seems almost too banal to observe that such an extreme preservation of Miss Begum's Muslim identity must perforce be at the expense of any British identity. Nor, incidentally, is Miss Begum "preserving" any identity: she's of Bangladeshi origin, and her adolescent adoption of the jilbab is a symbol of the Arabisation of South Asian (and African and European) Islam that's at the root of so many problems. It's no more part of her inherited identity than my five-year- old dressing up in his head-to-toe Darth Vader costume, to which at a casual glance it's not dissimilar.

Is it "bigoted" to argue that the jilbab is a barrier to acquiring the common culture necessary to any functioning society? Is it "prejudiced" to suggest that in Britain a Muslim woman ought to reach the same sartorial compromise as, say, a female doctor in Bahrain? Apparently so, according to Cherie Booth.

One of the striking features of the post-9/11 world is the minimal degree of separation between the so-called "extremists" and the establishment: Princess Haifa, wife of the Saudi ambassador to Washington, gives $130,000 to accomplices of the 9/11 terrorists; the head of the group that certifies Muslim chaplains for the US military turns out to be a bagman for terrorists; one of the London bombers gets given a tour of the House of Commons by a Labour MP. The Guardian hires as a "trainee journalist" a member of Hizb ut Tahir, "Britain's most radical Islamic group" (as his own newspaper described them) and in his first column post-7/7 he mocks the idea that anyone could be "shocked" at a group of Yorkshiremen blowing up London: "Second- and third-generation Muslims are without the don't-rock-the-boat attitude that restricted our forefathers. We're much sassier with our opinions, not caring if the boat rocks" - or the bus blows, or the Tube vaporises. Fellow Guardian employee David Foulkes, who was killed in the Edgware Road blast, would no doubt be heartened to know he'd died for the cause of Muslim "sassiness".

But among all these many examples of the multiculti mainstream ushering the extremists from the dark fringe to the centre of western life, there is surely no more emblematic example than that of Shabina Begum, whose victory over the school dress code was achieved with the professional support of both the wife of the Prime Minister who pledges to defend "our way of life" and of Hizb ut Tahir, a group which (according to the German Interior Minister) "supports violence as a means to realise political goals" such as a worldwide caliphate and (according to the BBC) "urges Muslims to kill Jewish people". What does an "extremist" have to do to be too extreme for Cherie Booth or the Guardian?

Oh, well. Back to business as usual. In yesterday's Independent, Dave Brown had a cartoon showing Bush and Blair as terrorists boarding the Tube to Baghdad. Ha-ha. The other day in Thailand, where 800 folks have been killed by Islamists since the start of the year, two Laotian farm workers were beheaded. I suppose that's Bush and Blair's fault, too.

I'd like to think my "woolly liberal" colleague Vicki Woods and the woolly sorta-conservative Boris Johnson represent the majority. If they do, you've got a sporting chance. But in the end Cherie Booth and Dave Brown and the Bishop of Lichfield will get you killed. Best of British, old thing.