Even if you don't recognise the name Orla Kiely, chances are you know her designs. Notice the increasing number of colourful, retro-print bags slung over the shoulders of every 25 to 50-year-old with a passion for quirky fashion? They're hers. And, once you're aware of them, you won't want to escape the enticing world of design she's creating.

The Irish, London-based, designer's business has just celebrated 10 years in the fashion industry. Today, along with her world-renowned bags and accessories, Orla Kiely has a celebrated womenswear line, travel collection and homeware range – all boasting her signature chic, funky, feminine style.

This year, along with her two design collections, she's launching a stationery line exclusively with the Museum of Modern Art (MoMa) in New York. She's also doing her third collaboration with creative powerhouse, the Tate gallery, and is set to announce a joint venture with an ultra-upmarket furniture company.

"Each year, we do a new project," explains her husband, Dermott Rowan, who's also managing director of the company. "But we don't do anything unless it can be done absolutely perfectly."

"The whole thing started by accident. We had this chaotic situation where boxes of sample designs would come into our apartment and if we didn't get them out by 5pm, there was nowhere to sit."

Perfection is what Kiely is known for. She qualified as a textile designer from Dublin's National College of Art and Design (NCAD) before doing a Masters in knitwear at Royal College of Art (RCA) in London. Now, twice a year, she develops a unique print at her design studio in Clapham which is then stamped in various forms (discreet to less so) on her bags, knitted shift dresses, floppy hats, coloured tights, coats, mugs, rugs, wallpaper, lampshades and more.

Her inspiration comes from the 60s and 70s. "I'm inspired by anything from that time," she says, "but, as a designer, I also think it's very important to take something and then reinterpret it. So we always make our designs clean and modern and all about colour. We're about taking something from the past and moving it forward."

The 'we' Kiely refers to is her 40-strong team, but also her partnership with Rowan. Like other great matches in the industry – Dolce and Gabbana, Matthew Williamson and Joe Velosa, Alice Temperley and Lars von Bennigsen – Kiely and Rowan's is one made in fashion heaven.

It began when Harrods snapped up Kiely's collection of hats at her exit show from RCA in 1993. She worked and consulted for high profile companies including Esprit, M&S and Habitat before developing a capsule collection for Debenhams and launching her own business in 1997, helped by Rowan's financial controller background.

"Nothing was planned," he insists, "the whole thing started by accident. Orla was consulting for other companies and designing her own collection at the weekend, which she would give to me to organise. We had this chaotic situation where deliveries of her designs would come into our apartment and if I didn't get them out by 5pm, there was nowhere to sit!"

Together, they thrive. Orla as the hard-working designer and Dermott as the hard-talking businessman. In the time I spend with them, they finish each other's sentences, challenge one another and laugh together. This happens four times a week when they catch up on business over lunch (they don't discuss work at home with their ten and 12 year old boys) before going back to their respective responsibilities.

"I don't interfere in the design," admits Dermott. "He doesn't," seconds Orla. "I'm open to good suggestions but if they're not good….I dismiss them," she jokes.

"The car park print was one of our major prints at the time and I looooved it but buyers didn't like it. Two weeks into the season, they were phoning us saying 'we can't believe it, they're selling out, it's going mad'."

How long does it take her to develop a collection? "Eight weeks," he quips. "Dermott, do you mind?" Orla laughs. "We start developing prints in April and once we have that and the colours sorted, there's the design and other aspects. Ultimately, everything including sampling has to be finished in August, sometimes quicker because our factories need time."

Meanwhile, Dermott is flying around the world, selling the lines, negotiating business deals and opening more shops. Today, they have flagship stores in London (Monmouth Street), Hong Kong and Paris, 12 shops in Japan, a fast-growing export business to the US and Middle East, as well as website sales at www.orlakiely.com  which gets 700,000 hits a year.

Proud of the multi-million pound business they've built together, they're just as proud of how they've built it. "The growth has been phenomenal but very controlled. We still own the company 100 per cent which is amazing," he says.

"We've grown in a nice way, never overstretching ourselves, and we've been lucky with a following that seems to come back," Orla admits. "Our customers are into their style and find the designs accessible, whether they're celebrities or people of any ages.

"I actually got a magazine the other day which was guest edited by actress Kirsten Dunst," she continues. "And in a collage of her personal photos, she was wearing one of our dresses at a christening. I thought it was very us, very real life."

Even their mistakes are successful. "Do you remember the car park print," Orla asks her husband. "That's right!" he laughs, "we mis-registered on a print by half a millimetre and the Japanese rejected the whole lot. We had the same collection in Selfridges and it sold out in a week, so we put the products in there and it sold out again."

"That wasn't the story I was going to tell!" she laughs. "Before we had our retail shops, we would get feedback on different ranges from store buyers. The car park print was one of our major prints at the time and I looooved it. It was different and vibrant but the buyers didn't like it at all. So the figure and quantities we ordered were lower than usual. Two weeks into the season, they were phoning us saying 'we can't believe it, they're selling out, it's going mad'."

"There has to be a level of risk in fashion and I'm not afraid to try something new," Orla admits, "I think that's actually very important. We often look at things and think 'Ooooh, maybe that's not quite commercial enough'. But they're often the good ones, I think. They're the ones I like."

If there's anything to be gleaned from their success story, it's to trust what Orla likes. With her pieces renowned for being as beautiful inside as they are out, as quirky as they are chic, and with an ever-expanding audience who appreciate them, the future for their fashion isn't just bright, the future of fashion is Orla Kiely.

By Barbara Walshe