The radicalisation of some younger members of Britain's 1.5 million-strong Muslim community has led to often heated debate. Now questions are being asked about whether British-style multi-culturalism is succeeding or failing.
Protests over Rushdie's novel in the 1980s was a turning point
Muslims have lived in Britain for centuries, but only relatively recently have they become the focus of controversy.
Three big crises over the last decade and a half have heightened tensions between Muslims and non-Muslims:
- The Rushdie affair of the late 1980s
- The attacks of 9/11 in the US, and their implications for Britain
- And now, potentially most serious of all, this month's London bombings
They pose awkward challenges for British policy-makers.
The Rushdie affair was, in many ways, a turning-point.
Until then most Britons, especially in London and the prosperous south, had scarcely been aware of the new Muslim communities taking root in northern industrial towns like Leeds and Bradford.
The public burning in Bradford of Salman Rushdie's novel The Satanic Verses was therefore a huge shock.
The affair showed up the yawning gulf between Muslims, who believed the novel slandered their faith and its prophet, and a liberal intelligentsia outraged at the idea of banning, let alone burning, a book.
The Iranian death threat against Rushdie, which a few British Muslims supported, further polarised opinion.
The affair triggered the first serious debate about a community which was little known or understood.
Angry young Muslims
Large-scale Muslim immigration to Britain occurred after World War II.
Muslims from Pakistan, Bangladesh and India provided cheap labour for the textile industry in northern England.
The attacks in London have pushed the issue to the forefront
At first, they were unaccompanied men intent on earning money and then returning home.
But in the 1970s, they began to bring their wives and children to join them.
By the time of the Rushdie affair, they were starting to think of themselves as British Muslims rather than Muslim immigrants.
Although the campaign against Rushdie's novel was led by first generation community leaders, it also served to mobilise the disaffected young.
Politicians and commentators began to ask whether Britain was now home to a new generation of angry young Muslims.
A series of issues - both domestic and foreign - served to further radicalise Muslim opinion.
These included the Palestinian intifada, the Gulf war of 1991 and the plight of the Muslims in former Yugoslavia.
At the same time, many young British Muslims experienced a familiar mix of inner-city problems - crime, drugs, unemployment and prejudice.
Many felt prejudice was directed at their religion as well as their skin colour.
It was in this context that the attacks against New York and Washington took place on 11 September 2001.
This raised the alarming prospect that young Muslims living in the West might be susceptible to the radical and violent ideology of al-Qaeda and its leader, Osama Bin Laden.
Following the bombings in Madrid in March 2004 and in London on 7 July 2005, this question has acquired a new urgency.
Omar Sheikh (above) is in a Pakistani jail for the kidnap and murder of Daniel Pearl
Richard Reid is serving a life sentence in the US for trying to blow up an airliner
Saajid Badat was found guilty in the UK of conspiring with Reid
The possibility that the London attacks were the work of young British Muslim suicide bombers poses a significant challenge to Muslim leaders and the Blair government.
Muslim parents, teachers and community leaders are under pressure over whether they have done enough to acknowledge and tackle the threat of extremism.
British politicians are not only having to review domestic security.
They are being forced to think again about the mix of liberal policies pursued by successive governments since the 1960s - collectively known as multi-culturalism.
Multiculturalism was designed to bring different communities together, but its critics argue it has only served to keep them apart.