When the latest series of BBC's Dragons' Den hit our screens in July, it featured the biggest shake-up of the panel of investors the show has seen in its 10-year history. Out went Piers Linney, Kelly Hoppen and the long-serving Duncan Bannatyne, and in came Moonpig founder Nick Jenkins, retail entrepreneur Touker Suleyman and food-and-drink businesswoman Sarah Willingham.

Willingham is perhaps the least well known out of the three, but it is her appointment that might just prove to be the most significant. The show has featured women in the past, including Deborah Meaden and, more recently, Hoppen but has not featured a working mum since the days of Rachel Elnaugh, who left after the second series back in 2005.

Willingham is a welcome example - both for the television series and for business in general - of someone who has built up a successful business empire and career while juggling parental responsibilities for her four children, aged eight, seven, five and four. It is a constant battle to find the right balance, she says, and has sparked a number of pivotal decisions in her career, including her rejection of the corporate career she had carved out with Pizza Express at a point when she had yet to meet her future husband, let alone think about having children.

"Everything is done thinking about how it will impact the family and me as a mum," she says. "The times it goes wrong for me are when I'm not enough of a mum, and when I feel that my business world is taking me away from my core, which is my four great kids.

"My mum was a teacher so she was around a lot and a lot of the formative parts of my life - the very fundamentals of who I am and some of the big decisions I made - were me coming home from school and going through things with my mum. I want to be that mum; I know that in 20 years' time I will not look back and wish I'd invested in another business or spent more time working. I'm very conscious of that on a daily basis."

Lure of the den

It was this concern which made the BBC's offer to feature on Dragons' Den harder than it would have been otherwise for someone whose focus since selling the Bombay Bicycle Club chain of Indian restaurants in 2007 - again as a result of the need to focus on her children - has been on investing in small businesses with the potential to grow.

"People think it's a complete no-brainer; it's not," she says. "With filming, I'm away from home for quite a long time and when you have four kids aged eight and under, it's not a given. It has to be something that is really worthwhile for you to want to put that strain on the family. But because we were doing all our investing exactly at that stage, it fitted perfectly. I was going to get 20 days with over 100 pitches while I just sat in a chair. You can't say no to something like that."

With the series still being aired, Willingham is unable to say much about the investments she has made on the show, although there are a few, and she admits that on occasion she has been more attracted by the personality of the entrepreneurs than the business concept itself. "There were a lot of incredible people who walked through the door and that's what surprised me more than anything," she says. "But first and foremost it's all about the person.

"There were a couple of people who just walked through the door and as soon as they started pitching I thought "I couldn't work with you" because of the way they answered questions and how defensive they were," she adds. "I'm very much no-ego in business; there is no place for it. We've all got to be open to very honest feedback.

But you'll see throughout the series that some really great people with pretty average products get investment because they are so back-able, and we'll find the business model within it."

This idea of being open is something she believes essential in any investment, whether in or outside the den. "Whether the business has been going five years or five minutes, just be very open about where it is," she says. "Ask for help; say when you don't understand something. It's OK to not know something. That's a really important thing for anybody starting out in business."

She admits she was slightly unprepared for the combative attitude in the den; a style that does not come naturally to her, despite her explosive debut on the show. "I'm an extremely collaborative person," she says. "I thought that the whole point was that between the five of us we would unravel a business, but I'd completely forgotten about what would happen if all five of us wanted it. You soon work out that it is a bit of a poker game. Peter Jones usually shows his hand last, but it was also a lot easier for Peter and Deborah to win. There were some occasions where the new dragons beat the old dragons but there were a lot more where the old dragons beat the new ones."

Hungry for success

Willingham's own success as an entrepreneur is different to many, having initially pursued a corporate career that gave her the experience she needed to go it alone. There was always a desire to make money - she had childhood jobs delivering papers, working in a hairdressers and serving in a tea shop - but it was far from the stuff of entrepreneurial legend.

Her experience in the tea shop was formative, though, as it set her on the path to a career in the restaurant trade. "I loved the buzz and the social part of it, and worked in bars when I was 18," she says. "It was the usual stuff that people do but I'd very much found my industry. I was very good at front-of-house so I earned really good cash doing a job that I loved doing."

In time, she landed a job with Planet Hollywood, initially overseeing the opening of its restaurants on the Champs-Elysées and what was then Euro Disney in Paris, and later in its head office, taking responsibility for its European franchises. "There was nothing to not love about those jobs; I was in my early 20s and travelling all over the place, and for me it was much less about being an entrepreneur at this point in my life. I just loved what I was doing, I was learning and having a lot of fun in an industry that I loved.

"But very quickly at Planet Hollywood I realised that the business model was not one that was going to stick around," she adds. "I'd see what they were spending on the sites and what their turnover was, and it wasn't a sustainable model. But I loved the international side of it because I had lots of autonomy. I was effectively my own boss but within a corporate environment."

If her career up to then had been relatively conventional, the next step revealed the kind of get-up-and-go that would later shine through as an entrepreneur. She walked down the high street seeking food businesses that might be interested in international expansion, and approached both Pret A Manger and Pizza Express. "Pret A Manger said they weren't interested but Pizza Express said they'd just started to look at international expansion and offered me a job," she says.

Initially this involved looking after Europe but eventually expanded to all international development. "They had just sold the Middle East franchise and Moscow as well, and we expanded quite quickly," she recalls. But after a while she realised this was not core business for Pizza Express, and expressed her intention to leave, only to accept a position working for the board. "That was a really great couple

of years for me, because I worked very closely with a lot of very successful businessmen and entrepreneurs like Hugh Osmond and Luke Johnson, and during that period I actually got to the point where I thought I could do this," she recalls.

But it was one of her more entrepreneurial ideas that would sow the seeds for her eventual exit, after approaching the board with the idea of taking over the failing Indian restaurant chain the Bombay Bicycle Club. "I wanted to roll it out and do to Indian food what we'd done to pizzas," she says. "And they said "no, we do pizzas"."

Seizing the opportunity

She realised this was her opportunity to launch out on her own in a sector she already knew inside out, but was also driven by a realisation that a corporate career would be incompatible with her other ambitions in life. "I was also at a very critical point, as a woman in business," she says. "I was 28 and I hadn't yet met my husband but I knew that if I was to be so lucky I wanted to have lots of children. I realised that someone had always told me where I was going to be every morning, and while that had been great fun it was not sustainable if I wanted a family. That was a real turning point for me, when I thought if I'm going to have the life I want to when I do have a family I've got to do this. I can't continue to work for someone else."

Willingham set about raising the finance to buy the stricken chain, using her contacts in the industry to partner with The Clapham House Group. "Raising the money was just a question of making sure that I approached people who I had worked with and who knew of my skillset within the industry," she says. "That would always be my advice for people trying to raise money; to start very close to home. I'm not talking about family, but if you're raising money the chances are it's in a field that you know something about. It's so much easier to back people who have done it before."

What she found was a business with lots of potential but little in the way of processes and systems. She uses the analogy of moving it to one side and putting in place some solid foundations. "You start to understand where you make and lose money so it's about putting proper management account systems in and making sure that there is no margin for error on your food orders," she explains.

"I also started to standardise the kitchen; I don't mean you take the chef away but you do put some kind of process in so if the chef doesn't turn up it's not the end of the world. You start to standardise the costs; so what is your model, what works? You might open here with this rent, but what turnover do you get at that size? You start to look at what the optimal business model is going forward, and that could be everything and anything, from HR to paying the right wages." She estimates she lost around a quarter of the staff in the first six months as a result of the changes, but finally the business moved on to a more stable footing. 

In time, the business expanded to 17 restaurants across the country and Willingham had responsibility for other brands in the group, including Tootsies and The Real Greek, but by now she had had her second child and, once again, found herself putting family first. "With one child everything still seems possible, because they just come with you everywhere," she says. "When you have two it's a whole different ball game and I just had to be very honest with myself, and it was a very difficult decision. But I realised I couldn't be the mum I really wanted to be and have 1,500 staff. I just couldn't do it." She believes she could have opened another 50 restaurants had she stayed on.

Backing growth

But one thing she had learned was just where her real skills lay. "That's my niche; the middle bit," she says. "So if someone has created something which has legs, then I can take it to the stage where we prove it's got legs and then someone else can come along and take it to the point where it's got mass. I'm that middle bit."

Alongside her husband Michael Willingham-Toxvaerd, she has since sought out and invested in businesses with just that potential, including the nutrition health firm NeutraHealth - later sold to Elder Pharmaceuticals in India - the London Cocktail Club and the Craft Cocktail Company, as well as a hologram business called GrooveMe, alongside fellow investor Sir Bob Geldof, while also launching the money-saving personal finance website letssavemoney.com.

It was this background which made the call from Dragons' Den so hard to resist, although as she consciously scaled back some of her teams last year to "try and regain my life" she is also aware it could be a double-edged sword. "We really stripped back, and I did it to stop being accountable to so many people," she explains. "Obviously the more people you hire, the more rely on you. It's been brilliant; we have much more control of our lives and we're much more hands-on and understand the businesses a lot more.

"We're looking at two other quite significant investments outside the den as well, so we're suddenly going to have a slightly larger portfolio," she admits. "We're having to think about some of the types of investment that we make now, so they're not so hands-on and don't need so much of our time. But remember that there are two of us. That makes an enormous difference when you have a husband who does this full-time as well."

She is, though, slightly apprehensive about just what else the show could entail, particularly the potential for her own profile to increase. "I don't know if I'd be OK with it or not because it's not happened yet but I'm a very private person, which I know sounds ridiculous when I've gone on Dragons' Den," she says. "But I'm very protective of my life, so the thing I will fiercely fight for is that it doesn't affect or take away from our family life."

Her family life involves large amounts of cooking and also eating out regularly but their biggest indulgence, as she calls it, is travel. "We travel a lot, probably two to three months a year," she says. "We go away a few weeks at a time and completely reboot. We go all over the place; just this year we've been to Thailand, Africa, Denmark, France, Egypt and Turkey."

All in all, though, she's pretty content with where she has ended up, and particularly the balance she has been able to strike between her business career and personal life. "I'm very lucky that I can now afford to make decisions based on what I want to do," she admits. "I often think I could have more time with the kids and I often feel stretched. But I'm on a lovely path and if I can keep adding a few nice businesses to it where I'm not doing all of the work but I can dip in and out with my expertise I'll be happy. I just want to keep on enjoying the journey."