There were Irish and Jewish people in London in the 12th Century. Greek Street in Soho takes its name from an Orthodox community there in the 17th century, while the East End has played host to seventeenth century Hugenots, eighteenth century Irish and 19th-century Jews before becoming the Bengali community it is today.
And work by the London Research Centre published this week, based on the 1991 census, shows the process is still at work. From 20 per cent of the population now, ethnic minorities are projected in just 15 years' time to make up 28 per cent of the capital's population.
Two London boroughs, Brent and Newham, will see the ethnic minorities become the majority, their present 45 per cent and 44 per cent rising to 52 per cent and 61 per cent respectively.
But in every London borough the numbers will rise, from Bexley and Bromley to Richmond and Sutton. Each of these outer boroughs at present has only a 5 or 6 per cent ethnic minority population. But each of which will see a similar 40 per cent rise to the rest of London, taking them close to 10 per cent.
The increase is almost entirely the result of the natural age structure, not the result of higher birth rates or continued immigration, according to the London Research Centre. Those groups which will enjoy the highest rate of growth at present have the lowest age profile. According to Herman Ouseley, chairman of the Commission for Racial Equality, these changes represent both a challenge and an opportunity. By 2011, well over half London's ethnic minorities will be British born, a proportion that will continue to rise sharply as the wave of Caribbean and Asian immigrants from the 1950s and 1960s dies off.
London's cosmopolitan nature, however, comes not just from New Commonwealth immigration. In 1991, the census showed there were communities more than 10,000 strong in London from 34 countries. They ranged from more than 250,000 Irish to 133,000 people born in EU countries, 32,000 Americans, 50,000 Cypriots, almost 12,000 from Vietnam, 18,000 from Hong Kong, almost 14,000 from Mauritius, 21,000 from Poland, 16,000 from Malaysia, a similar number from Iran and 20,000 from Turkey.
Not all of these will be British citizens and London's role as a key financial and trading centre has contributed to its ethnic mix - bringing in the Arabs in the 1970s and the Japanese and growing ranks of Europeans in the 1980s and 1990s - combined with Britain's traditional, if steadily more restrictive, role as a haven for refugees.
The most dramatic engine of the recent change in London's ethnic make- up, however, has indeed come from New Commonwealth immigration, starting almost 50 years ago when the Empire Windrush docked in 1948 with the first Caribbean immigrants brought over to boost Britain's labour force.
In assessing how well the capital has coped, Anne Page, chief executive of the London Research Centre, and Chris Myant, a spokesman for the Commission on Racial Equality, strive for a balance.
On one level the capital has adapted remarkably well. Only briefly in the 1950s in Notting Hill has there been anything in London that could fairly be called race riots: the 1980s riots in Brixton and at Blackwater Farm having causes far more complex than race alone.
None the less, immigration initially produced the growth in intolerance that almost every wave of immigrants has faced. Its peaks were symbolised by Enoch Powell's "rivers of blood" speech in 1968 and the growth of the National Front in the late 1970s and early 1980s.
But as legislation progressively restricted immigration, governments of both colours began to take positive action to promote good race relations with the result that London now has a record far better than probably any other European city, where in most cases mass immigration has been far more recent.
"The reason, I think, is that we deliberately faced the issues after the growth of intolerance of the 1950s and 1960s," Anne Page, the London Research Centre's chief executive says, defining the passage of the 1976 Race Relations Act as the crucial moment in that.
"As a result, London today enjoys a rich mix of people and culture unparalleled in Europe, and an atmosphere of racial harmony, compared to its own recent past and possibly to other large cities in Europe," she says.
Chris Myant points not just to the immense range of restaurants and shops reflecting flavours and cultures from around the world but whole ethnic shopping centres from Soho's Chinatown to Southall's Indian markets that are an intrinsic part of London life, as is the Notting Hill Carnival, a uniquely Afro-Caribbean event that draws in a vastly wider range of the population than Afro-Caribbeans alone. That, he says, "is very different from the odd Chinese or Japanese shop. These are real communities that are part of London and it is something that gives us great confidence and hope for the future."
There remains, he says, however, a darker side, one of unequal opportunities and uneven achievement, fuelled by continuing discrimination. There is a seemingly permanent undertow of racial attacks and violence in parts of London. Employment opportunities still vary widely by race. Among 16- to 24-year-olds, the Labour Force Survey showed last year that 60 per cent of black males were unemployed, a rate approaching three times that for whites. Average weekly earnings for whites in London are just under pounds 400 a week against not much more than half that figure for the ethnic minorities. And while a black and Asian middle class has emerged in growing numbers there are wide variations among the ethnic groups.
The 1991 census showed that among black Caribbeans, there were half the managers there would have been if there was no employment difference between ethnic groups: the figure for the professions being a third. By contrast, among Indians the proportion in the professions was higher than expected, although managerial numbers were relatively low. The professions employed almost twice as many Chinese as might be expected. Bangladeshis, particularly, were over-represented among unskilled workers. And despite considerable considerable efforts, the ethnic minorities remain under-represented across wide swathes of city life, not just in professions and top management. The Metropolitan Police, already policing a city a fifth of whose population is from the ethnic minority still has only around 1.5 per cent black and Asian officers.
If there is a long way to go to achieve equal opportunity, the continued growth of London's ethnic minority population, however, is surely less threatening to the white population now than the original immigration of the 1950s and 1960s. Familiarity has bred mutual tolerance. The National Front and British National Party, which once had their bases firmly in London's inner city, now seem to do better in Bexley where ethnic minorities still make up a mere six per cent of the population.
In an increasingly global world, London's cultural and linguistic diversity can be seen as a key competitive advantage, if only the capital has the wit to use it. "Britain's ethnic minorities are an irreversible part of the social, cultural and economic well-being of London," Mr Ouseley argues. "Employers in London have the opportunities to be the envy of the world with such diversity".
With more inter-marriage, more mixed communities, more ethnically mixed children and more diversity, London is set in the 21st century to become a new type of city for Europe - one more like the immigrant cities of the United States, but without, if London gets it right, their segregation.