Born in Poland in 1936, Barbara Hulanicki lived in Jerusalem as a child before moving with her family to Britain. She made her name with Biba, the cult fashion brand she started with her husband Stephen Fitz-Simon ("Fitz"). Epitomising swinging London in the 60s, the first boutique opened in Kensington in 1964 and was a magnet for stars including Twiggy and the Rolling Stones. By 1974 Biba had graduated to a department store ("Big Biba"). In 1975 Hulanicki left the company but continued to work in the fashion industry.

You're bringing out a book about Biba. After six decades in fashion, why now?

It's as good a time as any. But as with everything reflective, it's thrown up some emotional and upsetting events, which have nothing to do with Biba.

You fell out with the board and parted company in 1975. That must have been devastating. Is that what you mean?

That was one of them. It was a heartbreaking period. It's not that I don't want to discuss it, it's more that it's wiser not to. They are powerful people. But we [she and Fitz] ended up in Brazil, exporting clothes from there, working with other labels like Cacharel. It was different but exciting. Brazil is a wonderful warm place.

You're now in Miami, designing hotels. That sounds lovely.

Oh it is, the sun, the sea. It happened when I met Ronnie Wood at a party and he asked me to design the interiors for a hotel he owned in Miami. Then I met Chris Blackwell [of Island Records] who asked me to design a corridor for the Marlin in the 90s. That period was incredible. Chris knew everyone. I remember sitting at a party with lots of famous people and they put me next to a very quiet boy. Except, of course, it wasn't a boy, it was Prince.

You've been working nonstop since the late 50s. How much has fashion changed?

Fashion then was staid. The shows were so stuffy – Balenciaga, Dior even Givenchy. Big gowns. That was it. The last show I went to was Topshop. The music, the lights, it's all changed so much. But the thing is – you always feel like you're left out.

Was there a single turning point for you, career-wise?

Of course – Felicity Green at the Mirror [in 1963]. She wanted a dress for the fashion pages. So I made her a dress. It was £3, pink gingham, very short. I was terrified. What if she hated it? But she loved it, and it sold and sold. It came in one size – 8, I think.

Because one size fits all?

I know that sounds mad but girls in those days, there were no continental foods to get fat on, and no one did exercise, so they weren't muscly. Not like the American girls. We made a few pieces in a size 12 but no one bought them. Of course when the pill came in that changed everything. I remember crossing Kensington Church Street in 1969 and seeing these girls with their thighs and their hips, and thought: uh-oh. Now being thin is a status thing!

Biba sold the whole lifestyle: food, clothes, furniture. You were, to some extent, a prototype for Gwyneth Paltrow and her Goop lifestyle brand.

Ha, well, it was more practical than that. To me it was obvious to sell the things I needed. After all, I was a working mother. So we brought out prams and furniture and homeware. All you could get was old junk, the stuff that you pay a fortune for now. I sold butter, tinned peas and baked beans (my husband loved baked beans).

Were you driven by a desire to rebel?

Absolutely. Everyone wore coral lipstick, so we made chocolate brown. And, of course, the brown sold well. I've always been rebellious. You have to remember that in Palestine we all wore bloomers and smocks, all matchy-matchy, fashion born out of necessity. I wanted to do something different, to make beautiful clothes, like Audrey Hepburn in Givenchy.

You always wear black.…

I'm lazy, mainly, but also it means whatever I'm doing or presenting, I'm not the focus. I even designed black nappies for Biba – I wanted my baby, Witold, to look cool. But black – it was a no-no colour back then, so again I was rebelling.

I imagine being a working woman in the 60s also fed into that. Are you a feminist?

Yes, but a natural one. I was never used to men being around and I was fiercely independent. Men were disgusting back then. I was always going to work, mother or not, and we had a creche in the store but it wasn't "activism". It made business sense.

Biba had a famous clientele – David Bowie, Marianne Faithfull…

We had no PR, and we only closed the shop once, for Princess Anne. But when anyone famous came in we'd sneak them into the office at the back. Brigitte Bardot had just married Jacques Charrier when she came in. He didn't want her in the public changing room so we took her out the back. It was like a Dickensian scene – freezing, dark, dusty, a couple of guys playing cards on the floor, and there she is, starkers, in the stock room, oblivious to what's going on around her.

Is it true the changing rooms were unisex?

Not officially, but they became unisex when the New York Dolls came in.

Your life has been bookended by tragedy. First, your father's death [Hulanicki's father, a diplomat, was murdered by a Zionist extremist group in 1948 after the UN had decided to partition Palestine into Jewish and Arab states. He had acted as a mediator]…

That was a horrifying experience. I was 12, it was 1948. We were at the house, our bags packed when there was a bang at the door. I remember him walking past our bedroom and saying bye-bye, and that was the last time I saw him because the people at the door, the gangsters, took him outside, tied his hands and shot him.

Do you remember it clearly?

Like it was yesterday. I can't talk about it without getting very upset.

Then there was the death of Fitz in 1997…

My relationship with Fitz was wonderful. He had the business head, I had the designs. We met at a party in our early 20s – he was an advertising executive. His death was incredibly hard. One day he was fine. The next day he was in hospital in NY and a neurologist was telling us he had a few tumours and not much time to live. I was devastated.

But you have your son, who you are very close to.

Witold, yes, who I adore. He married a boy so now I have two sons. I was so terrified he would have a bad experience coming out but I think it was fairly painless and we're all very happy. I feel very lucky – I am in good health and I have a lovely life.

That's a very stoical attitude. You're still working now. Will you ever stop?

No, I intend to outlive you all.

The Biba Years is published by V&A