On a grotty winter???s morning in west London, Justin Thornton and Thea Bregazzi???s gorgeous home is a bustling haven from the spitting rain and grey skies.???Can you do me up????Thea laughs, beckoning her husband to deal with the delicate buttons of the diaphanous, daintily printed silk dress that she???s slipped intofor Stella???s shoot and swooshing herPre-Raphaelite auburn hair across one shoulder so he can see what he???s doing.

In between takes, the couple chat aboutthe morning???s news and their passionfor Victorian glass bottles (they are madfor all things Victoriana), while making cups of tea, which they serve in terribly refined teacups and saucers.In the almost 20 years since Justin, 46, and Thea, 47, began their Preen fashion label from a tiny flat (???the sewing machine was next to our bed???), they and their clothes have become much adored.

Their show at London Fashion Week is invariably packed with editors, stylists and buyers, decked out in their own Preen purchases ??? proof of the loyalty their designs inspire.???We???ve never been ???the next big thing??? with so much attention on us that it???s too much to cope with or live up to,??? muses a self-deprecating Justin, now ensconced next to his wife on the sofa in their airy, eclectically decorated front room.

???Samantha Cameron just rang us and said, ???Can I come to the studio and try on a few frocks???????Justin

Instead, word has quietly spread about their flattering cuts and brilliant ways with prints and colours, creating clothes that tread the perfect line between being wearable and making you feel special.Just like the dress Thea is wearing; it???s exactly the kind of thing you???d admire ??? and want to tap her on the shoulder to ask her where she got it ??? if you saw her in a restaurant.But it could also be appropriate for a parent???s evening or work meeting.

???Our customers have grown up with us,??? says Justin.???When we were hanging out in bars and going to festivals, it was all a bit more grungy.Now our life has changed ??? we???re staying in nicer hotels, going to amazing events but also playing with our kids.???

???We just think of our group of friendsand what they want [to wear],??? adds Thea.???Obviously we have some things that are made for the woman with the perfectfigure but there???s not many of them, soit???s part of our job to make things for ???real??? women as well.???Alongside their own evolution, the couple have noticed a shift in the way women dress.

???For a while, womenwere scared to feel feminine because they wanted to be seen as powerful,???Thea observes.???So it was a contrast to really say, ???Oh yeah, I am a girl!??? and celebrate that.???This experimental attitudehas won the couple some high-profile clients.Preen has been the label of choice for Samantha Cameron many times during her tenure at number 10, perhaps most famously when she chose an electric-blue shift dress with a splashy black print and shots of lime to accompany her husband to Buckingham Palace after he won the general election last May.

???She just rang us and said, ???Can I come to the studio and try on a few frocks??????? recalls Justin.Michelle Obama is another fan.???There???s never been a world leader???s wife who???s been so colourful and so vibrant,??? says Thea.???She???s been so influential in the way women dress.???Justin and Thea are particular fansof Mrs Obama???s refreshingly realistic attitude to her wardrobe.

???I got a picture through a while ago and she was wearing one of our outfits that she???d already worn two years earlier,??? he remembers.???I thoughtthat was amazing; my God, she must actually keep it in her wardrobe.???Last year, they were invited to a gathering of Mrs Obama???s favourite designers at the White House.???We were allowed two guests, so, of course, wetook our mums,???Thea smiles.???She was saying to each of them, ???I bet you???re one proud mom!??? and they were like, ???Yes,yes, we really are!?????????Sometimes I just think they have no idea what we do,??? says Justin, ???but when it???s on the cover of the newspaper or a trip like that, they???re really proud.???

Justin and Thea both hail from the Isleof Man where, it???s probably safe to say, fashion wasn???t a major presence in their early lives.In fact, it wasn???t until they started an art foundation course ??? which was where they met ??? that either of them realised that the job of ???fashion designer??? actually existed.

???I used to make my own clothes a lot of the time, or I???d go round second-hand shops,??? says Thea, who has retained a soft Manx lilt.???My friends andI would cut up things and make our outfits for Friday night.???Preen is known for bringing a diverse mix of inspirations to every collection.For spring/summer they looked at the costumes worn by Michael Clark???s contemporary dance company and Thea???s beloved assortment of antique Victorian blouses.

Justin puts this mish-mash approach (which always results in cleverly offbeat but elegant looks) down to their teen years spent hanging out in the ???only decent pub on the island???.???It was called Bushy???s and they played punk, goth, new romantic and popbecause everybody liked different things.I think that???s why we feel it doesn???t matter that our reference might be a weird goth/emo girl and a romantic novelist ???everyone can get along!???

The couple moved to London, got their design degrees and started out in fashion in the early ???90s, when the capital was buzzing with a far more haphazard kind of creativity than today???s slick operations.Justin was working for designer Helen Storey, while Thea dabbled in freelance styling and design projects.When Storey asked them to make some pieces together, they realised that their partnership could be not just personal, but professional, too.

They went into business in 1996 and soon expanded from their flat to a shop in Portobello, which is now the stuff of fashion legend.???Portobello was a really happening place,so people used to just come and hang out and we didn???t take anything particularly seriously.We just made things to go out in,??? remembers Thea.In fact, they quickly built a reputation for unique pieces, withCher and Janet Jackson among theirearly patrons.

The couple could even claim responsibility for Kate Moss???s famous love affair with skinny jeans.???Thea really wanted to wear drainpipes so we just decided to make some,??? says Justin with a shrug.They were a big hit, selling 30 pairs every weekend (a lot for a business where everything was made in the back room of the shop).???They were really hipster and skinny.Kate Moss would come in and buya few pairs at a time,??? says Thea.

When they started to show at London Fashion Week, a draughty warehouse in east London with no heating was their only option, so they bought foil blankets for everyone who came (which would constitute an Instagram moment now).After a few seasons they moved to New York, which proved a major turningpoint for the business, as buyers from the international stores didn???t reallycometo London in those days.

It was in 2012 when Thea was pregnant with their second daughter, Blythe, that the time was right to come back to London Fashion Week.She was due to give birth two days after the show, so flying outwould have been impossible.???I???d actually done New York alone before [when Thea was about to have their eldest, Fauve] andit was so weird that we said never again,??? says Justin, shuddering at the memory.By then, London Fashion Week had becomea much more polished affair and everyone was begging them to ???come home???.

Now three and seven, their daughters have helped them ???rebalance???.Of course, they love visiting their parents??? studio after school or at weekends.???A couple of summers ago, we were working on this collection with lots of beading and bright colours,??? says Justin.???Fauve loved all the sparkle and was pinning bits on the mannequin.Then she saw the show and afterwards she said to us, ???I???m glad you had my dress in the show.???Ah, she was so proud!??? laughs Thea.

The girls have also inspired a spin-off line of childrenswear called Mini Preen.Each super-sweet piece ??? from embroidered cardigans to delicately pretty organza dresses ??? is a scaled down or adapted version of items from the main collection.

???Our customers have grown up with us.We just think of our group of friends and what they want???Thea

The sofa they???re sitting on for our interview is also scattered with bold cushions in some of their signature prints, a bowl on the kitchen shelf jangles with the fruits of their new foray into sunglasses and even their phones are encased in Preen print covers.Happily, it???s all available to buy via their treasure trove of an online shop ??? visit at your credit card???s peril.

The couple admit that life with kids, a business and countless creative endeavours (they do interior design for friends here and there too) is a ???roller coaster???, but escaping to their cottage in Suffolk keeps them sane.???I know a lot of the fashion crowd go partying in Santorini,??? says Justin, ???but with a three year-old and all those steps, you???dbe in A&E before you know it!Much better to go to our bolthole and just relax, read a book or something.???