Likewise, there is something otherworldly about Bella herself. She exists on a different scale and at an altered pace. She is slight, but not remarkably so, yet somehow, sitting on the sofa in her front room, she seems dwarfed by her surroundings. Everything, even the books, ordinary paperbacks, assume Alice in Wonderland proportions. She is pushed for time - she has an appointment in the West End just after midday – but our exchange is relaxed, no frenzy or pressure. The other meeting might as well be happening in a different dimension.

On the morning of our conversation, Bella is wearing jeans with some kind of complication in the pocket area, a red and white striped jersey top with a 70s-style long collar, a tailored pin-stripe jacket and grey felt Yves Saint Laurent platform sandals, “like little chairs”, worn over stripy socks. She looks springy and boyish, but also just a little louche. It is a fabulous combination. For all she is from a different planet, her fluency with the commonly spoken language of clothes is apparent. 

“I have always used clothes, even as a child” says Bella, “I remember being about nine, seeing myself in a mirror and thinking, ‘Stupid, I look like a pirate,’ then changing my clothes, and going, ‘Yes, I’m me again, I am the part of me that I want to show.’ I could change my clothes and feel that whatever was wrong had been masked.” For Bella, “the function of clothes” is “they make you feel control, and once you feel control in a good way, you can relax and be yourself. If you are not in control of your clothes, you are exposed, people can see into you.”

The source of Bella’s craving for a sense of control isn’t a mystery. Recorded in her sister Esther’s novel Hideous Kinky and subsequently made into a film, the itinerant, unsettled nature of her childhood is well known. Moving to live independently in London aged only 16, her immediate ambition was to play in a band, but Bella recalls, “Whatever it took, being a musician, although I used to practice the guitar, I never pushed myself the extra step to actually do it.” Instead she cut her hair short, hung out in the right places, and was offered a job at Vivienne Westwood and Malcolm McLaren’s shop Seditionaries on the King’s Road.

It was 1977, the heyday of Punk. For most of England’s youth, it was a chance for rebellion, but for Bella it was an opportunity for relative conformity.  “Punk Rock that was a kind of uniform. You put it on and it did something. I liked that about it,” she tells me. “Working for Seditionaries, having the best clothes, it really helped. If you were feeling gauche and idiotic, you could stay behind these incredible clothes and people would respond to you in a different way. They would be impressed. It was protection, bluff. It allowed you to make your way in the world.”

Bella is famed for her love of uniforms and there are often uniform-like touches in her collections. As a child she attended an alternative, Steiner school that had a uniform, but abolished it almost immediately on her arrival. “I had to pretend that I was glad, because that was the fashion,” she remembers, “but actually I bitterly wanted to wear one.” This love of regimented dress is not, however, the unqualified admiration of the sartorial disciplinarian. “I saw with school uniform, the minute you adjusted it, the minute the tie was slightly undone, it looked completely, wonderfully disheveled,” she says. It seems she craves restriction and rebellion in one.

“I like the way a tie and a shirt make a face look,” says Bella, “It is all about framing the face. When I got into fashion, I quickly became interested in Edwardian dress, a kind of closed body topped with an amazing face. You see that in the work of painters like Manet, even when his subjects are naked. Like Olympia, her body appears kind of closed, because she has the thin ribbon round her neck. That’s all she has but somehow she’s dressed.” Relating this to her contemporary designs she argues, “Now, although I am pretty much just doing jumpers, for me it is still all about framing the face.”

Designing her first collection in 1990, Bella quickly succumbed to the cycle of fashion. “Once I started, I soon realised that you had to do this is order for that to happen, that you had to have all the pieces to get the end result. It was a slave driver, but for me it was almost like, ‘Phew, I have found a discipline.’ There was always something to be done, but you have to do it, and then you get something at the end.” Although she hasn’t done a catwalk show since 2000, she still relishes the rigor of producing a regular if small collection of knitwear pieces. “It is my statement: here I am, these are my thoughts,” she explains. “If you make clothes, they don’t really exist until they are worn. An idea atrophies if it is not turned into something tangible.”

“Fashion has changed so much, there is room in the business now for people to work in all sorts of ways,” Bella says. “I wonder if its because fashion is so much more fashionable,” she ponders, “There are more people buying into it, in the old days most people bought clothes and a few people bought fashion, but now it is completely normal for everyone to buy it.” Bella has also kept herself on people’s minds with her recent Sunday Telegraph beauty column and the perennial popularity of the ‘Ginsberg is God’ sweater. 

Asked about the famous phrase, she laughs. “I was creating a story about these chicks who are waiting for their poet hero to come and do a reading, but he never shows up. Beatnik is always really good in fashion, it is so hilarious. I had all these names, Camus, Godard, Ginsberg, and I was trying to find out how it could work. Then the stylist Cathy Kasterine said, ‘Why don’t you do it like, Clapton is God: Ginsberg is God,’ and I realised I had been complicating things too much. My assistant Cozette had a cold, and she said, ‘Yes, Godard is Dog, I mean God.’ And that was exactly it. There was so much crap going down. Of course part of that was about breaking up the establishment, but any old person came out with any old rubbish, and only some of them were brilliant. I am not particularly into Ginsberg, he doesn’t really interest me, but it is a great name, and it captures a moment, and it looks right. And the whole thing about fashion is how it should look.”

If this sounds superficial, in a sense it is, but Bella takes surfaces very, very seriously. “If you have the surface right, then the rest can happily chug away. You have to get it all sorted on the outside, before you can relax into the interior.” Of course, all this talk of insides and outsides, what is shown and what is concealed, evokes the shadows not only of her father the painter Lucian Freud, but also of her great grandfather the pioneer of psychoanalysis Sigmund Freud. Bella doesn’t dwell on her amazing ancestry, but she has recently taken a position on the board of the Freud Museum, Sigmund Freud’s own house in Hampstead. Soon, as well as gazing in awe at the original psychoanalytic couch, visitors will be able to buy a t-shirt designed by Bella in the shop.

Just before noon, our conversation meanders toward make-up, and appreciating the point of it more and more. She highly recommends Charlotte Tilbury’s stuff, and is equally enthusiastic about Charlotte Tilbury herself. “She is so funny,” she begins, “if you meet her, you must get her to tell you about when….” 

But then her phone rings, and she realises she has to fly. 

The rest of sentence is lost in the fissure between Bella’s universe, and reality.