Ask him why he would not cheat the colour line and eat in white-only restaurants and his answer is simple: "What would be the point? I couldn't have gone with any of my friends and when I got there I wouldn't have known anyone."

His skin may have been closer in shade to those of his oppressors; but the experience in which he was rooted was not.

It is a powerful illustration of how little race has to do with skin tone and how much it has to do with power, history, culture and economics. Race is not a concept rooted in scientific reality - recent evidence suggests there is more biological difference within races than between them - but a construct. It is a way of understanding a reality that we have built.

The more warped the reality, the more grotesque the construct to explain and enforce it. In apartheid South Africa, babies were subjected to the pencil test. Officials would run pencils through their hair. If it stuck, their hair was curly and they had black blood and would be classified as such. If it fell out, their hair was straight and they were of pure white stock. It was a simple means of deciding whether your life would be destined for opportunity or damned by oppression.

So when it comes to race, black is, and always has been, a political colour. Its shade is not fixed but fluid and determined not by concrete rules but by specific contexts. Since the 70s, the dominant view among activists and many race thinkers has been that when it comes to British politics the term "black" covers all those who are not white, including Afro-Caribbeans, Africans, Pakistanis, Bangladeshis, Indians and Chinese.

That did not mean that all ethnic minority groups shared the same cultural values, social mores or even political outlook. Those who came from Barbados, for example, were likely to be embroiled in a culture clash with people from the nearby Caribbean island of Jamaica, let alone someone who came from Bangladesh or Burundi.

But while the different minority ethnic groups rarely mixed socially, they nonetheless laid claim to similar experiences. For the most part they came from ex-colonies, they were invited to take on low-paid jobs that white people would not do, they were concentrated in poor areas where resources were scarce and they had to endure the same levels of racist hostility in everything from the health service to policing when they arrived.

Metaphorically, and in some cases literally, they were all in the same boat. So while there were significant differences and occasionally even antagonism between them; these paled into insignificance when compared with the gulf in experience between them and the predominately white population into which they had settled.

Even if they did not identify themselves as black, it was a meaningful political expression to describe a common, non-white immigrant experience that went beyond the semantic. Black sections grew in the Labour party and trade unions, demanding greater representation for non-white people. And each one emerged with common demands for equality in the workplace, justice before the law, defence against racial attack and social investment in the areas where they lived.

Recent events in Oldham, Burnley and Bradford indicate that it is time to revisit the term "politically black" and ask if it remains a useful tool for describing the growing and fractured complexity of the British racial landscape. Not because the issues affecting non-white people have necessarily changed, but because they are impacting on different ethnic groups in such radically different ways that it may no longer provide a useful means for understanding the current race debate.

The divergent experiences of Indians and Bangladeshis provide a useful example. Those of Indian origin, according to government and independent statistics, are the most likely to vote, have considerable savings or achieve top exam results of all ethnic groups, including whites. On all these fronts, Bangladeshis are at the bottom of league tables, with Pakistanis not far behind. To talk of an Asian experience, let alone a black one, in that context is meaningless.

Health statistics show similarly wide discrepancies. According to the social trends survey, Caribbean women are far more prone to obesity than any other ethnic group - eight times the rate of Chinese women, for example. Meanwhile Bangladeshi men and women suffer disproportionately from being underweight.

The figures are endless but all paint a similarly varied picture that would increasingly make talk of any one common racial narrative increasingly problematic and misleading. There is not one politically black British experience but several.

Take Burnley and Brixton. Burnley saw the migration of Bangladeshi people who came to work in mills and factories. With the collapse of manufacturing over the past two decades, they have found themselves, along with many of their former white colleagues, out of work in a depressed northern town.

With house prices in the area for the most part stagnant, those who arrived 30 or 40 years ago are preparing to retire with no job and little in the way of savings. The future, for their children, looks bleak.

Brixton, meanwhile, saw the arrival of those principally from the Caribbean, many of whom found work in the public sector. Notwithstanding the savage cuts that took place over the Thatcher years, they found themselves in a region, the south-east, that has been in economic overdrive.

House prices have shot up. Their children are still far more likely to be unemployed than their white counterparts, but their prospects are brighter than those in the former mill towns of the north.

It is a crude comparison but an instructive one. The clashes of the past few weeks show there is an urgent need for the debate to shift, both in language and focus, if it is to remain relevant and pertinent. They also indicate that term "black" has far too often been used as a shorthand for Afro-Caribbean men in who live in London.

That does not mean that we want to hear less about them. This is not an argument for scrabbling over a tiny patch in political discourse but widening the terms of debate to fully accommodate the experiences of women, Bangladeshis, Pakistanis, Indians and those who live in the north.

Unity among those minority ethnic groups is a vital precondition to combating racism in this country. But it must be forged from reality; not proclaimed from abstraction.