Mark Selby looks tanned and relaxed after a 6-week sabbatical in Brazil. Who wouldn’t? The co-founder of Wahaca, the 11-strong Mexican street market restaurant group, says his current demeanour and state of calm is a far cry from what, looking back, he says was probably the most difficult point in his career, about three a half a years ago.

In the space of three weeks he opened the Soho restaurant, became a father, moved house and had the general manager of the new Wahaca resign.

Judging by his appearance now, it is hard to imagine Selby being wound up, but he says he found it a very stressful time. Again, who wouldn’t?  “But then, of course, you have to get on with it and within five or six weeks it was all fine again,” he recalls.

By his own admission, Selby is not the best at dealing with imperfect circumstances, something he attributes to his financial background, having spent the early part of his working life at Merrill Lynch, the financial management and advisory company.

“In banking everything has to be 100%. One of the hardest things for me to learn [about the restaurant industry], was that you can’t get it right all the time – someone somewhere, perhaps a chef, maybe having a bad day and you can’t control it. Now I know that you might be brilliant 95% of the time, OK 4% of the time and that for 1% you might get it totally wrong.”

He can’t quite fully accept this formula for reasonable expectation but has taught himself to stand back a bit and not try to fix everything: “I have quite a short attention span and I tend to look for things that are bad and how they can be better rather than looking at all the things that are good. I know, therefore, that I am not particularly good at managing people.”

Selby’s self awareness has led him to concentrate more on overseeing the business in terms of funding, site finding, brand development and design while his business partner, MasterChef winner Thomasina Miers, is responsible for developing and maintaining the quality of the food.

While things may not be quite as frenetic for Selby now as during that period when the Soho site opened, he certainly has a fair bit on his proverbial plate. Not only is he father to a three-year-old daughter and one-year-old twin boys, but the firm has just opened its first takeaway burrito outfit, Burrito Mama, next to its latest restaurant at One New Change, St Paul’s. Selby reports it is trading very well, with its City clientele embracing such a different lunch time option. While the concept is now ready to use in bespoke situations where the right opportunity presents itself, Selby stresses he has no intention to “enter the burrito war in London.”

In addition, Wahaca “will probably be going to Brixton, where most chains wouldn’t go”, and plans to open its first restaurant outside the capital within a year – potential locations for the 6,500-7,000 square foot venue include Cardiff, Manchester, Brighton and Liverpool.

“We were always scared of losing quality control, but we have brought people into the business with experience of running operations outside London,” Selby says.

A totally new concept is also on the cards for the next 12 months, although Selby is not giving much away: “It will be a smaller Mexican concept (about 2,500 square feet), standalone, with a little bit lower spend per head. It will be a quicker experience but not a takeaway (although there may be an element of takeout).”

Also, within the next six months, Wahaca hopes to launch a loyalty scheme with a difference, using its pioneering pay at table phone technology currently being trialled at the Islington restaurant, of which Selby says: “It is taking out the most frustrating bit of going out for a meal – getting and paying the bill.”

“We are looking at how loyalty schemes work and to shake it up a bit,” he adds. This kind of boundary pushing is typical of the Wahaca ethos. Experimentation is in the company’s DNA – like its two food vans and the shipping container ‘pop up’ restaurant on London’s Southbank, which has recently had its life extended.

Wahaca has also famously been at the forefront of the sustainable restaurant movement, right from the opening of its first restaurant in Covent Garden in 2007. There is no hint of ‘holier than thou’ about this, just a genuine belief that it’s the right thing to do, for many reasons 

“It has been important to us both [Selby and Miers], since the beginning. We could charge lower prices if we didn’t focus on it, but we just felt it was our responsibility to go down this route and that it was the way things were going anyway.

“It doesn’t matter to us what other people think – we know certain people admire us and probably a quarter of the people who come to Wahaca care about these things and about a tenth of them are passionate about it. We don’t think people come to our restaurants because we are sustainable.

With comprehensive recycling strategies, ecological building methods, its support for campaigns such as the Pig Idea (to lift the ban on feeding waste food to swine) and initiatives such as installing water efficient showers to encourage staff to cycle to work, it is no wonder that Wahaca was named Sustainable Restaurant Group of the Year by the Sustainable Restaurant Association in 2012 and 2013.

Selby says the company constantly challenges itself in all areas, from restaurant design to food development and technology to ensure Wahaca keeps ahead of the competition. “It has always been the culture of the business – it gives us more headaches that way but we have just got to do it,” he says.

Selby’s constant strive for innovation seems to be what really drives him, though, and always has. From a young age, Selby felt he would one day be running his own business and had always been drawn to the “theatre of restaurants”, which combined his personal passions of acting and eating. Once he had decided that the world of corporate finance at Merrill Lynch was not for him, although his time there ticked the box in terms of giving him the corporate and financial skills he knew he would need, Selby wrote to a number of entrepreneurs that he admired asking for a chance to join them, hoping that his big idea would soon come to him. Stelios Haji-Ioannou responded positively and Selby ended up working on new and largely unsuccessful concepts including easyCinema, easyPizza and easyInternet.

“It was an amazing experience working with someone with a lot of money who wants to try things and doesn’t get too stuck into the detailed business model. In his mind, one in ten of the ideas might succeed,” Selby says.

His easyExperience came to a natural end around the time of the failure of easyInternet, when an entrepreneurial friend of Selby’s introduced him to Robby Enthoven at Nando’s. Selby ended up working on the strategic and finance side of the business around the time of the creation of Gondola Holdings, in which Nando’s owner Capricorn Ventures was a shareholder. His employers of three years knew of his intentions to go it alone at some point, which turned out to be roughly when Gondola was floated.

A stint of inspiration-seeking travelling led him to Mexico and the light bulb moment when he realised that good Mexican food had not been brought to the UK. A contact hooked him up with Miers, who had lived in Mexico, and off they went together around the country refining their idea to a medium casual Mexican street food concept. Thanks to their experience of working with him at Nando’s and Gondola, Capricorn and Ask founders Samuel and Adam Kaye decided to back the duo, even though Selby is sure they didn’t really think the concept would take off.

“Mexico is one of the most bio-diverse countries when you think that things like corn, cocoa and avocadoes are all indigenous - it is an amazing country; such a rich culture. We spoke to lots of people about Mexican food and they all had quite strong views – they either loved it or hated it, which was great because at least they weren’t indifferent. However, most people thought it was all about cheap fajitas and sloppy food.”

Selby and Miers’ took about 18 months to find the Covent Garden site – much to Selby’s wife’s dismay, he cried when his first restaurant opened but wasn’t moved to  tears when his first child was born.

The Wahaca team’s inexperience of operations at the time made for an overly busy and understaffed debut restaurant unable to deliver consistent quality, but they tweaked as they went along and the site, as has been well documented, the site became fantastically successful.

Capricorn’s arm’s length approach to ownership is a perfect fit for Selby’s entrepreneurial approach to developing his restaurant chain and the private equity firm’s support has been rewarded with a successful business which generated turnover of about £22m last year and now has 650 employees and an average of 4,000 people a week eating in each of its restaurants. The funding and structure, including a recently introduced area management layer, are now in place to take the chain to 20 to 25 sites, after which it should be self-funding.

Selby hopes to always have some involvement in Wahaca. And it comes as no shock to hear that at some point in the future he would love to develop a totally new concept. He will.