Rebecca Gonsalves on the fashion designer, 69 today

London has a reputation as a breeding ground for young fashion talent: designers who are angry and edgy and loud. It's perhaps surprising then that Margaret Howell, one of our best-loved and most successfully exported designers, is none of the above.

While those angry young things are hell-bent on tearing up the rulebook every season, showing clothes that pack a punch, Howell takes a far more restrained approach. Her womenswear shows have famously occupied the same Sunday morning slot on the London Fashion Week schedule for years, and is frequently housed in her sky-lit store-cum-studio in Wigmore Street. Even before the first model steps out on to the catwalk, those present know what's coming: an unassuming colour palette, something of the sea in a summer collection, or of the countryside in a winter one, and all quintessentially British without ever resorting to pastiche.

Howell's fans are usually of a creative, independent bent, much like the woman herself. In 1969 she graduated from Goldsmiths College with a degree in fine art, after which she began making accessories – which took off after being featured in Vogue. Inspired by an old pinstriped shirt, Howell began the 1970s as a designer of men's shirts, later doing so for the likes of Ralph Lauren and Paul Smith.

The British business grew steadily. She teamed up with one of the 1970s' most revolutionary retailers, Joseph Ettedgui, to open a shop on South Molton Street, and introduced a womenswear range in 1980. In 1982 Howell expanded into Japan, where her unpretentious aesthetic struck a chord; she now has over 90 stores there in addition to those in London, Paris and Florence. More than just clothes, she sells a lifestyle: ercol furniture, anglepoise lighting and Robert Welch cutlery can be found among the crisp cottons and fine-gauge knits.

Howell's collections are always a continuation of what has come before – this is not someone who believes in blank slates every season, or that something considered beautiful mere months ago could become anything but, purely because of the passage of time. Indeed, her aesthetic has a soft, lived-in quality that means her garments only improve with age – handy, as they don't come cheap. And nor should they. µ