The saleswoman-cum-entrepreneur operates a boutique on Jermyn Street in London--that city's Savile Row for shirting--and has staked a claim in a business that has long been dominated by men.

"It's still an all-male club," she said of London's haberdashery market, whose marquis brands, including Turnbull & Asser, Hilditch & Key, John Lobb and Dunhill, were all founded and named for men. "But I think the notion that men only want to be dressed by other men is old fashioned. Men have very willingly accepted the product."

Sold online at EmmaWillis.com, in her boutique and at Selfridges, Willis' shirts, offered off-the-rack and bespoke, have become favored by luxury-seeking Londoners in the past nine years.

Now Americans will have their first taste of her ready-to-wear collection this holiday when it launches at Saks Fifth Avenue, where it will go up against men's names like Hugo Boss, Robert Graham and Paul Smith.

Willis acknowledged the discrepancy between women's wear--in which men lead the industry's design and business affairs--and menswear--which has few female brand names and executives in its ranks. But she said that belies a natural advantage women have in dressing men.

"When it comes to appearance, men often trust women more," she explained. "As well they should. It's us, after all, that they're trying to impress."