Margaret Howell started her business in the early 1970s and has become known for her high-quality men’s and women’s clothing, as well as her enthusiasm for British modernist design. She lives in south London and Suffolk.

Morning routine I get up at 7am if I’m going swimming, which I do two mornings a week, 7.30 if not. I like the morning when I’m completely on my own and have my cup of tea, homemade muesli and fruit. I put Today on the radio, and usually pack my lunch. Then I get the train to Charing Cross and walk to the shop in Wigmore Street.

Exercise routine I feel very irritable if I don’t do anything. I cycle and swim. I used to go to a proper gym club, where we would do apparatus work, asymmetric bars. We had a strict Czechoslovakian teacher and she was so hard on people they wouldn’t stay long.

Favourite piece of furniture It’s very difficult to say favourite, but the first piece of modern furniture I bought 30 years ago was the Mark Stam chair. It was the first cantilever chair in chrome and black leather, a very simple design. It will never date. I’ve also got a Le Corbusier chaise longue but it’s in storage at the moment because you need a bigger space. We bought it when I was pregnant with my daughter and I think I lay on it once. But it is beautifully worn in because the children used to slide down it.

Films you love One film I’ve seen more than any other is One Flew Over the Cuckoo’s Nest. Whenever it’s on television I get riveted again. A recent film that was good was Red Road – it had a very filmic subject: a CCTV operator. It made you think about it the next day.

Book by your bed Alan Bennett’s Untold Stories. I could re-read him a lot. He writes beautifully and somehow you know exactly what he means.

Essential gadget The coffee grinder, as I always appreciate having fresh coffee. I’m not a very gadgety person. I really like the Bang & Olufsen radio I bought about 20 years ago. It’s such a slim design and the sound is good. I used to take it when I went on country holidays in self-catering places with the children. Another thing I’ve had about 30 years is my Braun liquidiser. I’ve just ordered some replacement parts for it. I met Dieter Rams, who designed it, before Christmas and that stimulated me to make inquiries. He also designed the Vitsoe shelving system, some of which I have in Suffolk; it still looks so modern and works beautifully.

Most useful possession I love my bag that I bought in Japan. The concept is great. It’s recycled tarpaulin and the strap is a seatbelt.

How do you relax? I love long walks. Walking on an empty beach or through the country is very therapeutic. I had a lovely week walking the South Downs on my own, staying with friends on the way or in B&Bs. By the end of it, when I was going to come home I thought, I want to keeping going. It’s addictive.

Best present received The Nikon camera that my exhusband Paul gave me, I think for my 40th birthday 20 years ago. Although it weighs a ton, I still use it a lot. It doesn’t let me down. I’ve always taken photos. I remember on a school trip to France taking lots of pictures of fields of crops with my first Kodak box camera.

Favourite room I don’t really have one here. My house in Suffolk is 1960s, designed by a Swiss architect, and the study room has a corner window. It is lovely to sit there and work with the view and the window open during the summer. Finding out about the architect John Penn really came about through my move to Suffolk. There was a house by him down the road from me that I passed many times and adored. He built just nine of these small houses in a 10-year span, all of them very modern – flat-roofed, lots of windows, a nice flow of space. He is not very well known; he is quite a quiet man and gave up on architecture to turn to painting.

Oldest item in your wardrobe I could never get rid of those early things we produced, like the first linen jacket I made, because it was made at a time when I was just starting, working in my bedroom with my first machinist. The whole thing was from the heart and all-consuming.

Interview: Naomi West