The British home secretary, Charles Clarke, yesterday ordered the extradition to America of a British Islamist to go ahead – the first time a British citizen has been ordered to be extradited on terrorism charges. The case has been brought under a new fast-track extradition law that came into force last year.

Barbar Ahmad, a computer technician from Tooting in South London, is accused by American authorities of running American-registered Web sites and sending e-mails since 1997 in which he allegedly supported terrorism, encouraged Muslims to train for jihad, and solicited donations of money and equipment for a training camp in Arizona.

This decision sets a precedent and was not taken lightly. Mr. Ahmad, who is appealing the decision, has the support of the influential Muslim lobby, which has run a campaign on his behalf: petitions and protests in public, political pressure in private.

The member of Parliament for Tooting, Sadiq Khan, immediately denounced the decision, claiming for Mr. Ahmad all the rights this fanatical advocate of Sharia law holds in contempt: “It can’t be right for a British citizen to be treated in this way,” Mr. Khan expostulated.

Mr. Ahmad reminded us what he thinks of British citizenship in a comment posted on his Web site (yes, he still seems to have access to the Internet): “This should only come as a surprise to those who thought there was still justice for Muslims in Britain.” His wife told the BBC that every Muslim was now being treated as a terrorist and was at risk of extradition to America.

By braving the wrath of Muslim politicians in order to abide by its new legal obligations, the Blair government is signaling that Britain – unlike some of its European partners – is serious about cooperation with America in the war on terror. If Mr. Clarke had yielded to pressure in the Barbar Ahmad case, extradition of Islamist terrorists to America would have become a dead letter.

Much is made in the press of two facts: First, Mr. Ahmad might be treated by the American legal system as an enemy combatant and therefore risk the death penalty; second, under the new rules, the American authorities do not need to present formally a prima facie case for extradition.

But these arguments are specious. The Bush Administration is well aware of European sensitivities about the death penalty, and has given assurances that terrorists extradited from the European Union would not be executed. On the second objection: If there were not strong prima facie evidence to support the extradition, the case would have been thrown out by now. The evidence has been subjected to lengthy and meticulous scrutiny, first by a British court last May and then by the home secretary, who has considered all the evidence presented by Mr. Ahmad’s lawyers. His appeal will now be heard by the courts, probably up to Britain’s supreme court, the House of Lords.

A more substantial objection to the present situation is that there is no reciprocal American law to fast-track the extradition of terrorist suspects from America to Britain. The historic sympathy of Irish Americans for the Irish Republican Army and the strength of the Irish republican lobby in Congress have made it politically difficult for any administration to pass reciprocal legislation.

Even so, the British Government’s decision to start extraditing Islamists across the Atlantic makes this a good moment for Americans to revisit the question. Since 9/11, the IRA has been a busted flush in Washington. The British Government is not seeking to extradite any former IRA terrorists from America, and it is unlikely any new law would be used for that purpose. Nor does Congress want to be seen as soft on terrorism. If the State Department’s impressive new assistant secretary, Colleen Graffy, is to succeed in her long overdue task of public diplomacy here in Britain, then an offer to make extradition agreements fully reciprocal would be an excellent start.

Americans may have formed the impression that the British capital is such a hotbed of Islamist terrorism that it deserves its nickname of “Londonistan.” At times, it does feel like that. Not a day goes by without disturbing signs of the failure to integrate the fast-growing Muslim minority.

Yesterday, a report on the BBC mentioned, quite casually, that about half the Britons of Pakistani origin are married to their first cousins – a practice that is, I believe, illegal in America. British Muslims constitute a worryingly inward-looking, embittered, and backward minority that is rapidly falling behind other minorities, including Afro-Caribbeans, in educational and professional achievement.

The government’s response has been to set up committees of “moderate” Muslim leaders to make constructive proposals. This exercise has so far produced the fatuous idea of a state-funded “imam road show,” but there is fierce resistance to any suggestion that radically anti-Western imams should be weeded out of British mosques. Yet though some of these extremists are funded by the Saudis or even more dubious sources, quite a few are paid for by the taxpayer.

One of the neighbors on my street, as some readers may recall, is the most notorious Islamist cleric in Britain, the one-eyed, hook-handed Sheik Abu Hamza, former imam of Finsbury Park Mosque. For more than a year, the Egyptian-born cleric has been in custody, fighting extradition to America, where he is wanted on terrorism charges that include setting up a training camp in Oregon. He is also charged with terrorist offenses here in Britain.

In London, many houses and apartments in affluent neighborhoods are owned by city hall. This includes Mr. Abu Hamza’s house. Since his arrest, his home has been lavishly renovated at public expense. His wife and numerous children are thought to be living on social security.

Last week, we heard that a new neighbor just moved into our street. He is the latest addition to Prime Minister Blair’s Cabinet: the secretary of state for work and pensions, John Hutton. Whether the real estate agent told him who might be greeting him across the garden fence before he bought the house, I do not know. But there is a nice irony in the fact that Mr. Hutton is living right next door to “Hooky” Hamza.

Perhaps now that cabinet ministers find Islamist clerics literally in their own back yards, something will be done about “Londonistan.” Don’t bet on it.