Late one evening this summer, a taxi slips on to an empty dual carriageway. The driver leans back in his seat. “They came here to work and they didn’t like it at first,” he says. “They wanted a shag and they made the mistake of bringing their women over. Then they were stuck here and they got used to it. My grandfather tried to go back before he died and he couldn’t stick it.”

His grandfather was a Pashtun from northern Pakistan, one of thousands of workers who journeyed from the Indian sub-continent to West Yorkshire in the Fifties and early Sixties, answering the call for labour from the wool mills. The taxi driver has three children. One is safely established in a respectable career, the other two are works in progress. “I don’t mind my kids having the odd drink,” he says. “But getting p***** like the lads I pick up... And the drugs! Muslim kids on drugs! Twenty years ago, if there was one Asian Muslim in Leeds Prison it would’ve been a scandal. Now, it’s full of Asians. It’s like they’ve adopted the worst bits of British culture.”

We are on the way to Dewsbury in West Yorkshire, on a five-day trip to meet some of the worrisome youths of this latter British Asian Muslim generation. It ought to be said right now that on the way into this subculture of gangs and knives and drugs, I met many charming, well-adjusted teenagers and young professionals. But they were not the ones I had come to see.

“Are you CID?” the taxi driver asks. A lot of people asked this. I thought it unlikely that the police would send hapless white men with note pads to infiltrate Asian gangs, but it was a particularly fraught time in a particularly anxious town.

Following the murder in May of Amar Aslam, 17, in a local park, a young Asian man and four teenagers were awaiting trial – it takes place in November. And a further Dewsbury teenager was already in court for his alleged connections to a group accused of plotting “violent jihad”. Alongside suspicions that religious extremists lurked among Dewsbury’s youth were broader concerns that the town was developing self-segregated Muslim enclaves.

Arriving in Dewsbury on a sunny Tuesday morning, the market is spread over the central square. Veiled women brush past shirtless white men in the corridors between stalls. It is the sort of sight that gives Chief Superintendent Barry South, head of the local police division, a sense of optimism. When I ask him, a few days later, about the progress of racial integration in Dewsbury, he says: “We have two or three prominent supermarkets. Look at the mix of people in those supermarkets.”

He seemed to regard shopping as the great hope for social cohesion, the one ideology that binds us. Looking around Dewsbury Market that day, I am hopeful, too. There are three stalls selling cloth for veils and shalwar kameezes: two are run by white non-Muslims. Another stall is selling T-shirts proclaiming the owner to be a member of the “British Drinking Team”. The Muslim manager of a fish and chip shop – Muslim fish and chips! – has bought one, because they were only £1, but conceals the message beneath his apron: a compromise between Yorkshire thrift and his faith’s prohibition of alcohol.

Just as I am coming to believe in the power of retail integration, I meet a sceptic, a middle-aged white lady who asks not to be identified, and talks quietly as groups of women pass by chattering in Punjabi. “How can you be integrated when you don’t go anywhere, you don’t join anything and you don’t speak to anyone?” she says. “You can’t have integration when your religion stops you.”

But if the view from outside Dewsbury’s Muslim community is of a closed-off Islamic monoculture, the view from within is far more confusing. Instead of one community you find many. Leaving the market, we go to meet Shahid (not his real name), a well-travelled, well-educated young man in his twenties who grew up in Savile Town, south of Dewsbury. “You have Gujaratis, Kashmiris, Punjabis, you have Pashtuns from Pakistan and Afghanistan,” he says. “Now you have Sunni Iraqis and Shia Iraqis and Kurds. You have all these different communities. Half of them have their own f****** mosque.

“Each mosque says you can’t go and pray in the other or you are kafir [an unbeliever],” he adds. “We’re in a situation where we have two Eids – the festival begins on different days in different mosques.”

If the religious leaders of Dewsbury are divided by clan, then the youth have fractured along similar lines. “J”, 24, grew up on one of the toughest estates in Dewsbury. “You know castes?” says “J”. “There are lots of them and they don’t like each other. You get involved in a gang just to take your caste forward. You are going to kick the f*** out of someone just to advance your caste.”

Biradari, the ancient caste system, arrived from rural Pakistan with the first wave of migrants, to be reconstructed on the streets of West Yorkshire. In Young, British and Muslim, Philip Lewis, a lecturer at Bradford University, notes that such ties have often become stronger in Britain: “Groups suppressed in their home country are free to organise themselves and assert their political and cultural identity.”

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