Back in its heyday, Birmingham’s famous Balti Triangle was home to more than 30 authentic balti houses, with an estimated 20,000 diners a week passing through during the boom years in the 90s and 00s.

But today just four remain, as economic pressures and changing culinary trends have led many to be replaced by takeaways and dessert shops.

Last year, Adil’s, a Balti Triangle mainstay often credited with inventing the dish, closed after 43 years when its owner retired and there was no one to pick up the reins.

“There are a number of things that have killed it off. When it became really popular, landlords hiked up the rents. And a lot of them are family-run and it seems the sons and daughters don’t want to know,” said Andy Munro, the secretary of the Association for the Protection of the Authentic Balti.

As part of an exhibition to celebrate the history of the balti he is planning for later in the year, he has photographed every place that used to be a balti house – many of which are now burger joints and dessert parlours.

“When I left home, I started eating curries because I wanted to have something different, and I’d never had that before,” he said. “Many people in the younger generation, they don’t want a home-cooked curry, they want something trendy, a burger or dessert. But these things go in cycles and I hope it doesn’t stay that way.”

The balti, invented in Birmingham in the 1970s, is defined by the thin steel balti bowl it is cooked and served in, rather than specific ingredients.

Munro had been working to secure EU traditional speciality guaranteed status for the Birmingham balti, although this was halted by Brexit. And he is now hoping to work with the city council on a local accreditation scheme through trading standards.

One of the last remaining balti houses in the triangle is Shababs, which is seeing booming trade despite the decline elsewhere – it is in the process of expanding to double its current 120 seats.

Owner Zafar Hussain – who took over the restaurant from his father and brother, who founded it in 1987 – said his customer base has changed in the past decade from predominantly white western customers to a much more diverse mix.

“There used to be a lot of pubs around here but over the years they’ve closed down, and these worked hand in hand with restaurants like ours – it was a busy night every night after the pubs closed,” he said.

“But the culture has changed. This area is not so much the Balti Triangle any more, it’s a food triangle. The balti houses have been replaced by different cuisines, but the craze now is these tea and dessert places, and there’s lots of burger places popping up. So we’re still busy, but we’re not balti.”

Azhar Mahmood has been serving balti dishes at his restaurant Shahi Nan Kabab since the late 80s, and said the area around him has completely changed as the balti houses have slowly disappeared.

“The difference between me and them is that their clients were all European, my clients are all Asians,” he said. “But it’s important to preserve the Birmingham name, the balti brand. Other places do curries but they’re not baltis.”

The Balti Triangle originated as a cluster of balti houses in an area just south of Birmingham city centre, sandwiched between Balsall Heath and Sparkhill and home to one of the largest Pakistani Kashmiri populations in Britain.

It flourished in the 90s and 00s, with extensive TV and newspaper coverage, a play at the Birmingham Rep titled Balti Kings, even a balti ice cream. In 2007, Rough Guides listed it at number 15 on a list of 25 things to do in Britain before you die.

Even today, the area still attracts plenty of tourists. “Loads of people travel for miles to come to the Balti Triangle, and I think they’re probably expecting to see a balti house on every corner. But it’s not like that any more,” said Munro, adding that there are balti houses popping up in other areas of the city.

“I think it does have a future, but we need to work to make sure it does. No matter what happens, the Balti Triangle is still where it was invented, you can’t take the away the history of the place.”