Susanne Deeken is the heroine behind the screen at many major labels. The freelance womenswear designer whom girls want to be and boys want to be with, she is intelligent and erudite, with a fashion handwriting – both personally and professionally – that would put many an editorial to shame. Deeken is one of life’s elusive panoplies – with nice shoes and handbags.

We’re sitting at a canalside café in East London on a Saturday afternoon, a place where the designer comes most days with Jodie, her Collie cross. Deeken is Consultant Designer to Marc by Marc Jacobs, amongst others. And just as with Marc Jacobs’ English Bull Terriers, Jodie does not wear a designer dog collar. Because she’s a companion, not a trinket.

Despite the fact that Deeken passes by this café daily and knows the staff by name, they’re oblivious this chic, chainsmoking German-Londoner – everything is punctuated with an elegant flick of or drag on a cigarette – is the insider’s insider; a shadowy figure with proper influence in the fashion industry yet without the attitude that goes with it. Walk down the street in any major city and you’re pretty certain to see a woman in a garment Deeken has touched, even if you don’t know it. She has created for labels including Ungaro, Valentino, John Galliano and Martine Sitbon, is strong and opinionated but never flippant or egocentric. She doesn’t mince around in a hooker heel or dress like either of the gruesome twosome from Absolutely Fabulous. Even though she is, absolutely, fabulous. Marc Jacobs knows it – for his Autumn/Winter 10 collection show, the designer asked Deeken and stylist Camille Bidault-Waddington, her close friend of 16 years, to walk the runway.

“Oh that’s funny,” Susanne smiles. Funny is a word you’ll hear a lot, a way of diffusing the tension of a compliment. “A week before the show Marc came upstairs, to where we work on Marc by Marc, and said: ‘Ah you and Camille! I want 20 of you and 20 of you’. We were like, ‘Ha! Very funny’. Two days before the show we wished him good luck and he said: ‘Don’t go! We still have to do your fitting’. I started shaking like a leaf, I was so nervous, thinking: ‘Shiiiit!’. I phoned Dennis [Schoenberg, Deeken’s photographer boyfriend] and he said just think of Jodie when you’re walking down the runway! That really helped. It was actually easy and really good fun. I didn’t want to leave the catwalk once I got on it, I wanted to do another one,” she beams. To be honest, she quite easily could – Deeken has appeared in campaign imagery for A.P.C, and is on the front cover of Wolfgang Tillmans’ bestselling Taschen tome with one of his muses, Lutz (as well as an art collection somewhere).

“It was very flattering from Marc, he is very generous and a great person – inspiring and clever,” she reflects. “I have great respect for him, he is so hands on and knows what he wants. His interest in the arts I love too. When I first started working there we used to have breakfast quite a lot at The Mercer and always be talking about music, art and dogs – he’s really into dogs as well. He’s so knowledgeable in many different fields. I appreciate the way he found fashion as the outlet for his creativity. He challenges himself and is a very nice person to be around. Very witty.”

If you work in fashion, you might want to cut out and keep that paragraph, such is the rareness of working for a company for over a decade and still being as valued, content and excited as you were on day one.

Susanne grew up in the north of Germany, “A small town called Lingen, it’s really boring,” she explains, drinking coffee as Jodie is surveying the towpath. “It’s great as a kid because it’s in the countryside, but as soon as you become a teenager it’s a total nightmare. And I always wanted to get out – from when I was three I had a little suitcase packed to run away. And I kept on running away. My Dad would collect me from the forest – ‘Oh here we go again…’. The suitcase was filled with underwear, coins and chocolate,” she says, amused, and perhaps a bit amazed by her enterprise. “I was always fascinated by gypsies and gypsy lives – my parents never moved house, so boring.”

A stint in Copenhagen, a city that remains close to Susanne, came as a teenager, where she studied Fine Art; painting and sculpture. She stayed three years. Then Berlin called but only for three months. “It was too dangerous – you end up just going out and not doing any work. I applied to do some evening classes at the Art Academy of East Berlin. It was 1990 and the wall had just fallen, I was the only West German girl in that class – I was like Morticia back then, really extreme. I came into the classroom and they looked at me like ‘Who the f– is that? What a freak’. We did lots of life drawing, colour, learning the basics in an academic way. I then applied for Saint Martins.”

Saint Martins was always on the cards. Back in Lingen, when Deeken was 12, her sister had a Scottish lover that brought a copy of The Face to the house. “It was one of the first issues. I sucked up the content for years; I knew every page of that magazine, every picture, didn’t really understand the language but I knew it was so different from other magazines. It was so inspiring to me, I knew I’d leave [Germany].”

Her time at Saint Martins is talked about in halcyon terms, the bundle of years producing those which define the industry now. Deeken’s era included Hussein Chalayan and Stella McCartney. “It was so great. In my year were designer Lutz, who Wolfgang photographed, and my best friend Richard – I met a lot of really talented people. It was quite crazy.” Susanne doesn’t mention the names you might be waiting for, because she doesn’t entertain any notion of hype.

“I’d say I learnt most from my peers, except for Howard Tangye, who was my drawing teacher. He was the biggest inspiration ever, so fantastic. [Charing Cross Road] was great too. Even though you had no tables, no space, you made do with things.” Her final collection was: “Very experimental, very angry and inspired by the forest,” she says, surveying a passing boat. “The music was Diamanda Galás and hard techno. [Laughs]. Kinky Roland did the mix for me. My thesis was The Demystification of the Female. It started with witchhunts and ended with [performance artist] Annie Sprinkle.” Deeken relays this anecdote with humour and objectiveness, having left that side of her character in the past.

We move on and continue to chat at Susanne’s house, which, due to its attention to detail, makes The World of Interiors look like 60 Minute Makeover. She is a collector of just about everything but it’s all arranged beautifully. Downstairs in her studio, drawing and research files line up just-so. Upstairs a glut of naïve paintings – not hers – hold a wall hostage. Her shoeboxes have accompanying Polaroids on the outside. On her kitchen table is an Hermès ashtray. “My house is my haven,” she says, unsurprisingly.

Deeken used to collect records but that ended violently. “Yeah, I was a real trainspotter, first edition this and blah, blah, blah. I had a big collection at the studio I used to share with Camille in Hackney, before someone broke in and took all my rare stuff,” she says, pissed off. “I had a lot of numbered discs from Coil – 1 of 20, 1 of 30, some handsigned to me – all stolen. Siouxsie and The Banshees that I’d been collecting from 1986 was gone. And they nicked the record player. That broke something in me and stopped me from really obsessing.”

She and Bidault-Waddington shared a band too, the brilliantly/filthily named Pearl Necklace. “Camille played bass, I played guitar and we both sang really badly,” she grins. “Julie Verhoeven was the drummer even though we never even rehearsed with her. It was a total shambles.” This was twelve years ago when the girls lived in Hoxton and Verhoeven Elephant & Castle. Did they demo anything? “Yeah, but we recorded it all on a dictaphone, like the one you’re using there. We never went to a studio yet had write-ups in magazines. We could’ve got big, but we were just crap,” she deadpans. “There was no concert, it was ridiculous.”

You might be surprised her band were ‘crap’ when you take into account Susanne is, since the age of five, a very accomplished pianist, playing concerts and even composing and publishing her own music. She is working on a grade eight piece, the highest level, by Russian-Armenian composer Khachaturian at the moment. Like her lost Coil editions, it’s not in the Top 10 on iTunes.

“The problem was I didn’t like guys my age who were playing classical music. They were so boring and dull!” Deeken exclaims. It explains why her partner Schoenberg has a touch more Alec Empire about him, in comparison. “The girls were all mother’s jewellery and Shetland jumpers,” she grimaces. “I was hanging out with punks and they were totally not into it.”

Talk segues naturally to Susanne’s own fashion and style which is: “Quite chic and wearable – what women want to wear. It’s about making women look beautiful and sophisticated, and not being worn by some crazy garment you can’t even move in. I want to enhance your personality rather than impose a different one on you.” A big vintage collector, with thousands of pieces in storage, her ethos is to combine elements of the past with what is contemporary. It needn’t be mentioned that underneath the chic, there’s a healthy dose of rebel.

Can we expand on the list of major labels Deeken has penned for? It’s a lot longer than the five mentioned. “No. I really can’t,” she defends. “You can just say I’ve worked for a number of ‘prominent houses’.” Contractually, the designer is often stopped from mentioning who she freelances for. “I have to be discreet.”

“But I can tell you that I saw a dog friend in the park near here wearing one of my tops, recently. That was quite weird,” Deeken muses. “Because my work life and my fashion life are so detached from my dog-walking life.”

“The most peaceful, happy moments are when I’m drawing and illustrating just for pleasure, it’s one or two in the morning and nobody is calling,” she shares, honestly. “You have this moment of complete and utter happiness. I think few people have the opportunity to experience this and I feel so privileged. A lot comes from my childhood, the fantasy world I lived in as a kid, running around in the forest. The older I get the more I realise that, my God, I’m so influenced by it. I mean, look around the room. The feeling in your chest of emotion [breathes-in and gestures]. It’s unexplainable. You don’t have it all the time but when you do… I’ve always experienced it.”

Aged six, Deeken began making fictional mail-order catalogues, called SuDe. “You could order women’s, men’s, children’s clothing, camping equipment (because we used to go camping), musical instruments and books,” she explains. “Everything had colourways, prices, numbers and all these slogans I made up. I still have them. I also have one for wallpaper I’d designed, where I’d made swatches. These books are exactly what I now present to my clients – but it’s not fictional anymore. I do now always what I’ve wanted to do, just in a more sophisticated, professional way.” It’s brilliant to see someone living their dream and not being all X-Factor about it. But then, there’s not a lottery of any sort here. Susanne is a grafter with talent, in a time where the art of shutting-up and getting on with it is lost. If you’re itching to add her on Twitter, don’t bother: she hasn’t got one.

The photographs accompanying this feature are by Paul Wetherell, who Susanne first met in 1991, at a pharmacy in Clapham. “I was really sick, in my pyjamas. He was assisting David Sims at the time and asked to take some pictures,” Deeken tells of their past, whilst her cigarette conducts the room. “We did a portrait ten years later. And now we’re doing this. You could say he photographs me once every decade…”