Think of Brick Lane and what images come to mind? For many people it will be the eponymous novel and the film which followed it. But for those who have lived or conducted research in east London for some time, Brick Lane is synonymous with the noise and aromas coming from the Indian and Bangladeshi restaurants, filling the air from late morning until the small hours of the day.

Once a Jewish high street, Brick Lane, which witnessed a massive influx of Bangladeshis in the 1970s and 80s, is undergoing another episode of significant transformation. The phenomenal success of a thousand or so small and large digital creative media firms, which has recently enticed global players including Google and Pearson into the area, means that Shoreditch is being touted as the "next Silicon Glen". This is not just because of the success of the ITC companies, but also because of the many unique retail outlets selling cutting-edge fashion and contemporary art, clubs and bars, which have prospered despite the recent global recession.

The overall effect of these changes is that Brick Lane is now visibly and sharply divided at the junction of Woodseer Street between the curry houses at the southern end and the clubs, bars, retail outlets and restaurants at the northern end of the street. And it is revealing that the very few Pakistani-owned leather wholesalers in the latter segment are steadily being picked off by white British and white European entrepreneurs who, unlike the Bangladeshis under significant pressure from local mosques and sections of their own community to conform to Islamic norms, have no qualms about setting up businesses where alcohol is the principal source of their revenue.

Yesterday saw the start of the annual Brick Lane curry festival, which will run until the end of September. The surrounding roads were closed to traffic and the restaurant owners were free to put tables outside their premises to take advantage of the fine weather. The mainly young white crowd undoubtedly enjoy the day – entertained by a Bollywood-style female dancer accompanied by the nine-strong Bollywood Brass Band as they consumed prodigious amounts of curry and lager before wandering off in search of some action in the bars of the Old Truman Brewery site.

The first licensed Indian restaurant in Brick Lane, The Clifton was opened in 1974 by Musa Patel, a Pakistani migrant. It had previously operated in the same name as a cafe since 1959, and was a favourite haunt of the Kray twins. The number of outlets grew slowly so that in 1997 the area was home to 10 cafes and restaurants. However, a change in local planning regulations in the late 90s has meant that today the number has increased to 49. This makes the area the UK's curry capital, just beating the Rusholme area of Manchester, which at the last count had 45.

But even if they advertise themselves as "Indian" restaurants, all but one of the eateries in the Brick Lane area are owned by Bangladeshis, either first-generation or British-born second and third generation, who for one reason or another are keeping the tradition going. A few cafes on Brick Lane and the surrounding streets, like Gram Bangla and Cafe Meraz, are dedicated to providing the sort of home-style food that first and second generation Bangladeshis crave, but the vast majority of restaurants are producing a standard fare of chicken tikka masala, lamb pasanda and king prawn korma for a predominantly white British and white European clientele. Given this pattern, where, as any marketing expert would rightly ask, is the unique selling point of any particular restaurant?

To answer this puzzle, I asked one of the most successful restaurateurs in Brick Lane why there wasn't more innovation on menus. Why not bring more of the traditional Bangladeshi dishes into the mainstream restaurants like the wonderful "staff curry" served to the kitchen workers and waiters at the end of their shifts? "We tried it and it didn't work," he explained. "Our people like their curries with a thin sauce, but English people like a thick gravy."

Other restaurateurs I spoke to at the festival flagged up a number of concerns. They were especially annoyed that Tower Hamlets council had allowed the proliferation of "world food" stalls in the Old Truman Brewery providing visitors with a choice of cheap Chinese, Sri Lankan, Thai and Vietnamese meals. "People can buy something for less than five pounds," said one. "It's killed off our normal business during the day on a Saturday and Sunday." Why doesn't the local authority consult and do more for the area, especially with the London Olympics due in 2012? "These people have no idea about business – for many of them getting elected is the first real job they've ever had," he replied. "They're happy being local celebrities and helping their friends, rather than doing anything constructive for Brick Lane."

Nevertheless, the change in the area might well be a sign of things to come. Only a handful of the Bangladeshi restaurateurs in Brick Lane own the freehold to their properties, which means that in the long-term they are vulnerable to more profitable enterprises moving on to their territory. But possibly the most important factor is that the restaurant sector has done its job by providing Bangladeshi migrants and their families with a significant platform for geographical and social mobility. Many restaurant owners and their families have moved to Newham and Essex, and it seems that very few young Bangladeshis now wish to work in the restaurant trade. Another successful restaurateur told me: "We will have 10 more good years but after that who knows? Many of us will have retired by then, so it will depend on our children and whether they want to work hard and do long hours." He paused and added: "None of my children want to follow me into the restaurant business – all the older ones have gone to university."