America, on the other hand, has always had large 'foreign' populations - indeed the US is founded on immigration. This is not to say that America is a worldy paradise for minorities (tell that to the black citizens of New Orleans) but it some ways it has its act together.

Europe, it seems, has done less than America to assimilate the children and grandchildren of newcomers. Why?

The answer depends on another question: what makes immigrants adapt? Some people stress the role of the host country, and argue that European policy has been worse than America's. Certainly, European policy has been all over the place. In France, anybody can be a citizen, and there are no recognised group identities. The ban on the Muslim headscarf in state schools exemplified this assimilationist tradition. Germany, until 2000, was the opposite: nobody could become a citizen if they were not of German extraction, even if they met the usual conditions (such as being born in the country of parents also born there). Britain and (until recently) the Netherlands were different again: they have sponsored a tolerant multiculturalism, in which minority groups are encouraged to celebrate their distinctiveness, so long as they accept that others can do the same.

After the events of the past two weeks, some Europeans are arguing that the British approach is the better one. Yet Islamic extremism exists in both integrationist France and multicultural Britain. Neither France nor Britain has avoided segregation in immigrant areas, although Germany has. America is moving away from multiculturalism, which dominated in the 1980s, to greater assimilation (some states ban Spanish as a language of instruction, for example). The correct conclusion is not that one model is best, but that policy may not be what makes the difference.

Since I myself could be regarded as a 'second generation immigrant', though having one British parent makes this categorisation complex, this is an area of particular interest to me. How is that I don't feel Indian at all, but consider myself UK through and through?

Charlemagne goes on to theorise on why some people 'integrate' more than others:

Work is the archetypal social activity. It provides friends and contacts beyond your family or ethnic group. If you start your own company, it pulls you further into the society around you. And here is a striking difference between Europe and America. Unemployment in France is almost 10%. Among immigrants or the children of immigrants, it is at least twice and sometimes four times as high. In contrast, unemployment among legal immigrants in America is negligible, and business ownership is off the scale compared with Europe.

The second big motor of integration is home-ownership, especially important in the second and third generations. This gives people a stake in society, something they can lose. Thanks to cheap mortgages and an advanced banking system, half of Latinos in America own their own homes. Britain, after its council-house sales and property booms, also encourages house ownership. In contrast, most of the blocks in the French banlieues are publicly owned.

Between them, a job and a house help to create not only more integration but also greater social mobility. Latinos supported America's turn towards assimilation because they feared the trap of Spanish-language ghettos. But the banlieues are full of people who have grown up without jobs, or any hope of getting a better income or a better place to live. For them, integration is a deceit, not a promise.

A job and a house will not solve everything. The father of one of the July 7th London bombers owned two shops, two houses and a Mercedes. But if you want to know why second- and third-generation immigrants integrate more in some countries than others, jobs and houses are a good place to start.

I think a third factor could be added to this - language. My experience of living abroad in China where my grasp of the language was basic to say the least taught me that without communication skills integration is impossible. Yet even some second generation immigrants in areas such as, say, Tower Hamlets in London, or Bradford in Yorkshire, don't yet speak English.

Then let's throw in a fourth - education. Education has a tendency to empower people, but without it the chances of unemployment and deprivation and alienation are compounded.

This may not necessarily be the case in France, but I think Charlemagne's analysis does not take every factor into account.