This may not come as a shock, but, according to industry figures, more than half of the UK's nightclubs have closed down in the last 10 years. Yes, clubs at the top end are going steady, electronic music is in boom time and drugs are reportedly the purest they've been for years, but in general, this is not a golden period for British clubbing.

It also won't come as a surprise to you that, pretty much in line with the decline of clubbing, another kind of nightlife in London and beyond is booming. A more social, and a more delicious kind. In 2015, it's no longer enough to serve up alcopops and cheap vodka and expect a crowd – the likelihood now is that if you're out and you're drinking, you're eating, too.

For the last five or ten years or so, the street-food scene has been changing the way we look at dining out at a breathtaking rate. Beginning in Austin and San Francisco in the US, and taking root in London, Leeds and beyond not long after, it's brought with it a massive influx in quality chefs cooking in temporary spaces, unhindered by huge restaurant overheads and liberated by an energy, a vibe – call it what you will – that's captured the imagination of vendors and diners around the world.

The backers

As well as the vast majority of its traders, the London Union project is backed by some of the biggest names in London food. Gizzi Erskine is among a list of supporters that counts Wahaca's Thomasina Miers, Times columnist Giles Coren, restaurateurs Stevie Parle and José Pizarro, and Soho House founder Nick Jones, to name just a few, among its ranks. "Jamie Oliver took about two hours to say yes," Downey says. "They were all on board with the vision."

With this in mind, what if we were to tell you that in the next five years, the biggest and best street-food event organiser in London will have built 15 new food markets in some of the capital's most underused, unloved spaces, and, to cap it off, created a permanent one the size of a football field, too?

This is the balls-out mission statement of London Union, the company created to absorb event organiser Street Feast and continue, and enhance, its work. It was founded earlier this year by Jonathan Downey – notorious in the industry for, among other things, setting up speakeasy Milk & Honey in Manhattan and Soho, and inadvertently kicking off London's cocktail revolution in the process – and Henry Dimbleby, Guardian columnist and founder of the Leon casual dining chain that now has 26 restaurants and counting under its umbrella. It's also got financial backing from industry figureheads such as Polpo founder Russell Norman, Nigella Lawson, Gizzi Erskine, Jamie Oliver and more. That's some serious clout to bring to the table. Or the street, as the case may be.

30 of our traders have invested in London Union and are share-holders, because they believe in it

So when we talk about this rapidly expanding company's plans for domination of London's semi-permanent food scene, it's not to be taken lightly. Since it came into the hands of co-owners Downey and Dimbleby, its rise has been monumental. Dinerama is packed out with hungry hordes as soon as it opens for lunch; Lewisham's Model Market feeds hangers-on till gone midnight; Dalston Yard, the company's first site, is still as popular as ever. So what's the secret?

"No one's done it before," Downey, known more commonly as JD, tells me when I sit down with him and Dimbleby at Dinerama, the first market opened specifically under the London Union banner, and a prototype in terms of the reclaimed-space model the company will work under. "No one's done a street-food arena like this anywhere in the world. It's not like we're opening a restaurant that's focusing on Japanese, or modern British, where there's a formula already."

The street-food insurgence was rumbling before the company's first site at Dalston Yard pushed it further. For Downey, the vital ingredient was something he specialised in: drinks. Bringing great bars – created and run by themselves, rather than outsourced to traders – to the market turned it from somewhere to eat dinner into somewhere to spend a whole night.

The two recognise that their company, back when it was called Street Feast, was the one to break the wave in London. But, they insist, they're not the ones to credit for the tens of thousands who come to drink and graze at its markets.

They believe the traders are the driving force, and always will be. Both Downey and Dimbleby are happy to wax lyrical about the chefs and traders they work with – whom they audition in a show kitchen at their office before they agree to host them at the market, and whom they and other industry figures mentor keenly. "When we set up this business, 30 of our traders invested and are shareholders in London Union, because they really believe in it," Dimbleby says. "Our success is down to the combination of having some really amazing traders to work with, plus JD's vision and them buying into that. That's what will keep us ahead of the pack."

"We need to make sure the quality and consistency is there, and people will come back," Downey says. "People make a pilgrimage from their office to come and eat here. People used to go to Pret, or Itsu, or Leon," he adds. "Now they're coming to Dinerama for lunch because they want Smokestak's barbecue, or Breddo's Tacos."

There's hay to be made, say the pair: without the costs associated with a restaurant, traders at London Union's markets can find themselves making superb money. "These guys are doing so well now in a semi-permanent or near-full-time space, they don't need to think about spending hundreds of thousands of pounds on a restaurant that'll just consume their lives," Downey says. "They can have a really good work/life balance doing what they're doing and take three months of the year off."

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"What we do is bring a crowd for them," Dimbleby says, "and if they're great, they'll make a lot of money and have fun, and all they have to worry about is their food costs and their staff costs. If you took a list of all the buzziest restaurants that have opened in London, I guarantee you can be making twice as much money as each of them.

"There are a lot of really talented chefs who've started a restaurant and are struggling to pay off their premiums. We would love them to see that, actually, there's an option to come to the street – it's a better life, you make more money, and you can do amazing things for an audience that is really enthusiastic and cares. I think we'll see chefs who thought that to be a chef you had to have a restaurant, that you can do it in a different way."

People used to go to Pret for lunch. Now they're coming to Dinerama

One obvious barrier to street-food domination, of course, is the weather. Dalston Yard, Dinerama et al may be more cosmopolitan, and possibly more European, than traditionally British, but they don't benefit from a European climate. "It's pretty risky to open a thousand-capacity venue with no cover in an English summertime," Downey says. "We need to make all our outside venues inside venues when it rains," Downey says. "As long as we've figured out how to do that without affecting the vibe, it becomes essentially a really cool food court."

So where does it end, I ask. Do they see a ceiling? All signs point to their gameplan being accomplished, and then some. Even without the enormous groundswell that means its venues are packed every night and genuinely loved by their visitors, money talks. This means that if, as Downey and Dimbleby are certain, there's more money to be made in street food than in restaurants – not to mention that, should their plan come off, there'll be more than five times the available real estate by the end of the decade – we may well see the tide change. Restaurateurs may come back to the streets. The whole food industry could see a palpable shift.

Downey's answer is simple: he points to the sky above Dinerama and tells me, "The only ceiling we need to worry about is the one we've got to put on this." ■

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