LONDON, Aug. 16 — When he converted to Islam six years ago, Nicholas Lock said, he faced two immediate difficulties. One was the aggressive skepticism of his father, an English professor and Oxford graduate who mockingly asked, “Do we have a convert on our hands?” and then proceeded to cook pork for dinner — bacon, sausages, chops — every night for a week.
The other, potentially more troubling in its way, was the greedily opportunistic reaction of various Muslim groups to Mr. Lock when he arrived at the University of Leeds to begin his studies that fall. They fell upon him as if he were a prodigal son.
“As a new convert, when you first become a Muslim, a lot of people try things out on you,” said Mr. Lock, 24, who also uses the Muslim given name Mahdi and runs a support network for Muslim converts in Nottingham. “They want you to come to this meeting, this talk. Certain radical groups want you because you’re impressionable, and it looks good to get white guys.”
Mr. Lock likened some of the organizations that approached him to cults, like Hizb ut-Tahrir, which says it is nonviolent but preaches the establishment of a caliphate, or pan-Islamic government, and has been banned from some Middle Eastern countries. “They think you don’t know anything, and they pounce.”
The potential vulnerability of converts to extremism — especially young men —is of particular concern now, considering that 3 of the 24 people arrested last week on suspicion of plotting to use explosives to blow up trans-Atlantic airplanes were converts. Neighbors and friends of the three have said that at least from the outside, it appeared that their transformations from aimless Western youths to highly observant Muslims were bewilderingly thorough.
One of the suspects, Abdul Waheed, whose late father was a local Conservative Party official, is said to have converted within the last six months, changing his appearance, behavior and friends, and marrying a Muslim woman believed to be from Morocco.
In addition, Richard Reid, the so-called shoe bomber, was a British-born convert to Islam who discovered religion while serving a prison sentence for a string of petty street crimes and muggings. He is currently serving a life sentence in the United States after being convicted of trying to blow up an airplane over the Atlantic by igniting explosives in his shoe.
There are no official statistics on how many converts to Islam live in Britain. Yahya Birt, a convert who is a research fellow at the Islamic Center in rural Leicestershire, puts the number at slightly more than 14,000, an extrapolation based on the number of people who described themselves as Islamic converts in the Scottish 2001 census (the census for England and Wales did not ask about conversion).
Clearly, only a minuscule percentage of converts turn to active radicalism, and there are many reasons for converting: an admiration of Islamic texts and practices; a desire by women to remove themselves from what they perceive as the aggressive sexualization of Western life; the countercultural rebellion of the younger generation against their parents’ liberalism; a sense of outrage at Western policy in places like Iraq and Lebanon.
But among young people in Britain, a common theme seems to be adolescent anomie, a longing for answers in a world full of intractable questions.
“It’s not a physical thing — it’s a passionate approach,” said Khalad Walaad, a spokesman for the Bradford Islamic Center, in the north of England. “When someone is looking for something, it’s us who can lead him as a human being.”
Myfanwy Franks, a researcher who has studied converts to Islam and is the author of “Women and Revivalism in the West: Choosing Fundamentalism in a Liberal Democracy,” said, “Being troubled does not necessarily lead people to conversion — people who aren’t troubled convert — but it could lead to extreme radicalization.”
Mentioning reports in the news media that Mr. Waheed was a heavy drinker and drug user before turning to Islam, Ms. Franks added: “I think there’s a tendency for some people, when they stop using some kind of addictive substance, to be left with a big hole in their lives. To do something extreme is the easiest way to go, because it fills that big hole.”
Britain has a number of well-known converts, including Mr. Birt, 38, who is the son of John Birt, the former director general of the British Broadcasting Corporation and who changed his name from Jonathan when he converted, 16 years ago; Joe Ahmed-Dobson, 30, the son of Frank Dobson, a former Labor health secretary; and the singer and Muslim campaigner Yusuf Islam, formerly known as Cat Stevens.
Perhaps the highest-profile female convert is Yvonne Ridley, a former correspondent for The Sunday Express who began studying Islam after she was kidnapped by the Taliban in Afghanistan in 2001. Now the host of a daily current affairs talk program on the Islamic Channel, Ms. Ridley, who wears a hijab that covers her hair and neck, said that Islam for her is a welcome antidote to Western libertinism. “What’s more liberating — being judged on the size of your I.Q., or on the size of your bust?” Divorced, with a 13-year-old daughter, she has stopped drinking and having flings. “I never sit in, waiting for the telephone to ring,” she said, “and I’m never dragged in to immaterial rows by inconsiderate, useless men.”
Many converts are apolitical, but for people like Ms. Ridley, who says that “this war on terror is a war on Islam,” religion is inextricably bound with politics. Increasingly, that seems to be the case, among Muslims in general, and among converts.
“It’s become much more political since 9/11,” Ms. Franks, the researcher, said.
Before Sept. 11, converts tended to discuss spiritualism and personal choice, she said, “but now they’re not talking like that.” She added: “I think there’s this polarization now. It’s like the middle ground has disappeared.” Where women once tended to wear head scarves — even in her hometown of Bradford, in West Yorkshire — she says that she sees many more in garments that cover their entire bodies, including their eyes. “It’s a political statement,” she said.
For young white men in economically blighted sections of the north, where jobs are scarce and disaffection is high, she said, Islam speaks to their masculinity, offering a place of refuge and a solid political base from which to reject their heritage. “The greater Muslim community is transnational and supranational,” she said. “It gives them an identify and a togetherness which is inevitably going to be against the West, because of their identity with other Muslims.”
Since the government began cracking down on imams who preach violent jihad against the West, many mosques have posted signs that expressly forbid political discussion inside. So recruiters who single out converts or the newly pious tend to do it on the streets outside the mosque or in universities and prisons, with their captive and impressionable populations.
“A lot of conversion happens at life changes, and there’s no doubt that you have radical recruiters who see new converts who come in to the faith as really good targets for their perverted ideologies,” Mr. Birt said. “The crucial thing is getting them near the time of their conversion, when they’re not settled in, where there’s a lot of feelings and emotions.”
Souad Mekhennet contributed reporting for this article.