Europe is home to a new generation of alienated young Muslims whose anger may turn to radicalism, the BBC's Islamic affairs analyst Roger Hardy finds in new three-part series.
Part one looks at the root causes of last year's London bombings and Paris riots.
Danish cartoons satirising the Prophet sparked furious protests
Shamsul Gani sits in his home, in the northern English city of Leeds, a proud father cradling his six-month-old son.
I ask him about the three young men from Leeds who carried out the London bombings last year.
"You'd have left your house keys with them and gone away for a year," he told me.
For many people, what motivated the bombers is still a mystery.
But Shamsul grew up with the three - all British Muslims from Pakistani families. (The fourth was a Caribbean convert to Islam.)
Shamsul admires the courage of Mohammad Sidique Khan, the leader of the group, even though he condemns what he did.
Khan left a videotape explaining his action as a response to Western policy in Iraq and other parts of the Muslim world.
"I have no reason to doubt the credibility of that tape," Shamsul told me.
"What you have to understand is his belief in what he was doing. He was prepared to put his life on the line for that."
Voices of alienation
My visit to Leeds marked the beginning of an odyssey in search of the roots of Muslim anger.
Western Europe is now home to some 15 million Muslims, most of them under 30.
Discontent among Muslims fuelled much of last year's French riots
Is a new angry, alienated generation of European Muslims now being drawn to radicalism?
That's certainly a widespread fear.
The London bombings were followed a few months later by the Paris riots. And then, more recently, the controversy over cartoons depicting the Prophet Mohammed. All these have reinforced that fear.
In the suburbs on the northern rim of the French capital, I found young Muslims, from Arab and African families, who feel excluded by the French state.
When during the riots President Chirac belatedly intervened, telling the people of the suburbs they were all sons and daughters of the French republic, many of them saw it as a bad joke.
France, unlike Britain, tries to keep religion out of public life. Everyone is supposed to be equal, regardless of cultural background.
Try telling that to Ali, who is 24 and unemployed.
"France has betrayed the young people of the suburbs. When you're called Ali you can't get a job. The French don't accept Islam. Politicians promise us mosques and so on, but at the same time they smear us and call us terrorists."
A double culture
I visited Clichy sous Bois, where the riots began after the accidental death of two teenagers during a police chase.
At a youth club, an audition was under way for budding stand-up comedians.
Britain was shocked that the 7 July bombers were home-grown
Fifou, a lively young French-Algerian student, did a sketch poking fun at the "double culture" in which she and her friends live.
At home they must be good Muslim kids; but outside they want the good life, just like their non-Muslim friends.
For a moment, I forgot about those thousands of cars, and hundreds of buildings, destroyed in three weeks of rioting last year.
But not for long.
Sitting in the youth club was Samir, a young activist who has set up a group to keep alive the memory of the two dead teenagers.
I asked him what his aim was. His answer: "To give voice to the pain."
There have been riots before, and nothing changed. This time he wants the message to get through.
Roger Hardy's three-part series "Europe's Angry Young Muslims" begins on the BBC World Service on 8 March.