There was nothing extraordinary, then, about the background of the London bombers. So why are these men, born and brought up in Britain, gripped by such a fanatical zeal for an irrational, murderous dogma, and seemingly possessed with a hatred for democracy and decency?

Muslims have been in Britain in large numbers since the 1950s. Only recently has fanaticism taken hold. The first generation of immigrants faced greater hardships and more intense racism than today’s Muslims do. Yet most thought of themselves as British and were proud to be here.

While that first generation often put up with racism, the second generation — my generation — challenged it head on, often leading to fierce confrontations with the police and other authorities. But however fierce those confrontations, we recognised that to fight racism we needed to find a common set of values, hopes and aspirations that united whites and non-whites, Muslims and non- Muslims, and not to separate ourselves from the rest of society.

It has been only over the past decade that radical Islam has found a hearing in Britain. Why? Partly because, in this post-ideological age, the idea that we can change society through politics has taken a battering. And partly because the idea that we should aspire to a common identity and a set of values has been eroded in the name of multiculturalism.

Over the past week, much has been said about the strength of London as a multicultural city. What makes London great, Ken Livingstone pointed out, was what the bombers most fear — a city full of people from across the globe, free to pursue their own lives. I agree, and that’s why I choose to live in this city. Multiculturalism as a lived experience enriches our lives. But multiculturalism as a political ideology has helped to create a tribal Britain with no political or moral centre.

For an earlier generation of Muslims their religion was not so strong that it prevented them from identifying with Britain. Today many young British Muslims identify more with Islam than Britain primarily because there no longer seems much that is compelling about being British. Of course, there is little to romanticise about in old-style Britishness with its often racist vision of belonging. Back in the 1950s policy-makers feared that, in the words of a Colonial Office report, “a large coloured community would weaken . . . the concept of England or Britain”.

That old racist notion of identity has thankfully crumbled. But nothing new has come to replace it. The very notion of creating common values has been abandoned except at a most minimal level. Britishness has come to be defined simply as a toleration of difference. The politics of ideology has given way to the politics of identity, creating a more fragmented Britain, and one where many groups assert their identity through a sense of victimhood and grievance.

This has been particularly true of Muslim communities. Muslims have certainly suffered from racism and discrimination. But many Muslim leaders have nurtured an exaggerated sense of victimhood for their own political purposes. The result has been to stoke up anger and resentment, creating a siege mentality that makes Muslim communities more inward-looking and more open to religious extremism — and that has helped to transform a small number of young men into savage terrorists.

There is nothing new, of course, in the use of terror tactics. What is new is the arbitrary, nihilistic brutality. In the past, whether we are talking about Palestinians hijacking aircraft or the IRA bombing British shopping centres, terror was always in pursuit of political or strategic aims. No longer.

The London terrorists — like those in Madrid, Bali and New York before them — issued no warnings, made no demands, left no list of grievances. Four men simply sneaked on to three Tube trains and a bus and without a word created carnage. For them, terror was an end in itself, not a means to an end. In this post-ideological age, few believe in political ends or have a vision of political change. Few actually believe in anything or can articulate what they believe in political terms.

All they feel is a sense of anger or resentment or rage. So terrorists just lash out. And without anything to believe in, without the moral restraints imposed by political activism, or the sense of responsibility to a cause or to a people, the unthinkable becomes possible. As in London nine days ago.

Kenan Malik is a broadcaster, author and lecturer