The Fashion Museum in Bath remains among this country's best-kept secrets.

As well as having a fine permanent collection of fashion and photography, dating back as far as 1600, the gallery is currently home to displays of wedding dresses (au courant!), the work of Helmut Lang (God), and, for the more historically minded, 17th-century gloves.

Then there's the ongoing Dress of the Year exhibit, which stretches back to 1963 and invites fashion commentators to choose one look that encapsulates a particular moment. The first, picked by the politely named Fashion Writers' Association, was a grey wool dress courtesy of Mary Quant. Since that time, Bill Gibb (1970, courtesy of Vogue editor Beatrix Miller), Biba (1972, chosen by Bobby Hillson, formerly head of the fashion MA at Central Saint Martin's), Romeo Gigli (1990, Browns' Joan Burstein) and Alexander McQueen (1999, me) have made the grade.

This year's dress breaks the mould somewhat as it was chosen by a designer for the first time – milliner Stephen Jones. His choice is a spring/summer 2010 Vivienne Westwood Gold Label dress (pictured).

Westwood, who turned 70 the day the dress went public, still cuts quite a grand entrance gown, and all while making her political views felt. Just now, the grande dame of British fashion is interested in protecting the planet and a DIY/make-do-and-mend aesthetic that is as fresh and innovative as it is gorgeous. Food for thought, then, and a million miles away from the obviously status-driven aesthetic that continues to dominate, albeit more discretely than it has done.

"I was amazed to see that the fashion doyenne, Vivienne Westwood, was not represented in the collection," Jones says. "For me, [this dress] represents the junction in her design oeuvre; the revolutionary ripped hems that she was the first to create 35 years ago in her punk clothing... The study of the ladylike design codes of the British Royal Family that started in 1985... The bicoloured taffeta draped in a radically unique manner which hints at decorum but with an underlying sexuality that is at the heart of Westwood's designs."

The lady is, Jones argues, "possibly the greatest designer of our times". And he's not wrong.