LONDON -- Ali Kasim, a PhD student from Iraq, hardly remembers the letter that came in the mail three years ago, informing him that he had become a British citizen.
But his wife will remember the moment she became British: At 3:25 p.m. on Friday, she stood at the town hall, swore allegiance in halting English to the Queen and all her heirs, and received a commemorative medal.
''I am now very happy," Zahira Kasim said, clutching the medal. ''It's very nice."
That American-style citizenship ceremony, instituted last year for the first time in British history, is part of a new push to raise the bar on obtaining citizenship, and to increase the sense of loyalty and belonging that Britain's burgeoning immigrant population feels for the United Kingdom.
In November, the government will require all new citizens to pass a ''Britishness test" demonstrating a minimum standard of English and knowledge of government practices, a move that officials say is also unprecedented in British history.
The push to raise the standards for citizenship has become more urgent following the deadly July 7 suicide bombings on London's transport system, perpetrated by the British children of Pakistani and Jamaican immigrants. A second, failed attack was carried out by East African immigrants.
Earlier this month, in a speech introducing tough, new antiterrorism measures, Prime Minister Tony Blair said the ''Britishness test" would be reviewed to see if it was strict enough. He listed it as one measure his government had taken against extremism.
The attacks have given a boost to conservatives who have long attempted to limit immigration.
''I think the government is listening," said Humphrey Malins, a Conservative party member of Parliament. ''It's really more important now."
The attacks have also put citizenship and Britain's ethnic enclaves in the media spotlight, as newspapers and opinion polls probe whether Britain's Muslim communities -- derisively dubbed ''Londonistan" -- have been integrated well enough into mainstream English life.
''I think there's clearly a big debate about what does it mean to be British and what sort of society do we want to be," said Andrew Dennis, head of research at Migration Watch, a watchdog group that researches and publicizes what it considers to be problems associated with the rising rate of immigration to Britain.
''I think Britain has steered a path of multiculturalism which has probably gone too far," he said, expressing his personal view rather than that of the organization. ''It has been almost sort of separate development that has been sanctioned. It's a voluntary apartheid."
Indeed, in London's East End, in the borough of Tower Hamlet, where a third of the population comes from Bangladesh, an immigrant can spend a lifetime without ever stepping far outside his or her own culture.
While many Britons celebrate this diversity as a part of what makes London special, social cohesion became a major concern four years ago, when race riots between South Asians and whites rocked the working-class northern town of Bradford, prompting the government to set up an advisory committee to study the issue.
''There was a problem that people were piling up in certain areas of the country and having remarkably little contact with other ethnic groups, including the majority of old Brits," said Sir Bernard Crick, advisor to then Home Secretary David Blunkett, who chaired the committee.
Crick's group recommended citizenship ceremonies, to make new citizens feel more welcome, and tests on the English language and basic government principles to ensure they had the tools they needed to begin a life here. The new requirements are far stricter than the old system, in which an applicant only had to get a community member to attest to his or her ability to speak English, and sign an oath of loyalty to the queen at a local notary.
The ceremonies and the new test have generated major debates, as conservatives advocated testing on tough questions about Britain's history and as some liberals dismissed the idea as silly and snobbish -- akin to the suggestion by Lord Tebbit, an adviser to conservative former prime minister Margaret Thatcher, that new immigrants only be considered British after they support Britain's cricket team over their home countries'.
Since the July bombings, the debate about social cohesion has become a debate over national security, as Britain's new citizens receive passports that enable them to travel with ease throughout Europe.
''Here's a large Muslim population that feels no loyalty to the UK," said Bob Ayers, a former American intelligence official who is now a guest lecturer at Chatham House, a respected British think tank.
In the Tower Hamlet registrar's office last week, M.D. Habibur Rahman, originally from Bangladesh, waited with his wife and three children for the 20-minute ceremony that would make him a citizen after living here for 25 years.
Across the room, Mariam Farah Goje, an older woman in bright scarves who came from Somalia six years ago, felt excited by ceremony, which she said makes newcomers ''feel important."
But to Rahman, 48, the ceremony seemed to be a kind of punishment.
''It used to be we were good. No questions. We received everything in the post," he said, recalling the simple process of taking his three sons' birth certificates to the town hall, and getting their certificate of citizenship in the mail.
''Now it's a bit difficult. The world is getting more tough. But if you want to live in peace, you have to accept all the rules, and I accept them."