By Louise Lague
May 06, 1991 12:00 PM

THE PHRASE BRITISH STYLE USED TO be easy to define: damp tweed and explosions of taffeta. But since she married the Prince of Wales in 1981, Princess Diana has helped transform English fashion with a dramatic, witty and yet veddy proper wardrobe that has given a fresh profile to English couture.

The genius behind the Princess’s tailored, tall and terrific look is an unlikely candidate. Catherine Walker, 40ish, considered by palace insiders to be Diana’s favorite among her stable of designers, is a rangy (5’10”) maverick who is—raise an eyebrow, please—French. “I never thought this was going to happen to me,” she says. “I’m privileged.” Walker’s success depends on both homework and whimsy. According to a close associate, the designer “has never put the Princess in anything that embarrassed her position, but just when you think you can predict what she’ll be wearing, there’s a showstopper.” Among them: a cheeky majorette’s outfit to greet King Fahd of Saudi Arabia in 1987, and a smashing kimono-style dress for last November’s visit to Japan.

Walker’s prices vary from $875 for a long wool-jersey jacket to $25,000 for a hand-beaded ball gown. Her Chelsea Design Co. also attracts Jordan’s Queen Noor and Michael Caine’s chic wife, Shakira.

Born near Boulogne, Walker—then Catherine Baheux—was raised by her mother, Agnes, a housewife, and a wool-merchant stepfather. After earning degrees in philosophy and aesthetics, she married London attorney John Walker in 1970 and learned about English “weekends in the country, golf, gin and tonic, and all that,” she says. Her husband’s sudden death of a heart attack in 1975 left her with two small daughters to care for. Making “bits and bobs” of clothing for her girls had proved so satisfying that Walker turned the wine store under the family’s Chelsea apartment into a shop selling her own maternity fashions and what she calls “Edwardian-cum-Victorian” children’s clothes, which were soon heralded by top fashion magazines like British Vogue.

She later dropped the smocks and branched out into day and evening wear for the nonexpectant. Since then, the business has grown to include 50 employees, a separate bridal shop and a line of swimwear.

Personally, says a friend, Walker is “the Greta Garbo of the fashion world.” She’s mum about her exact age and her very quiet romantic relationship with her business partner, Saaed Ismail. Rather than be seen at trendy restaurants, she takes her tea at the prosaic basement cafeteria of South Kensington’s huge Victoria and Albert Museum. “It’s down-market,” she says. “It makes me feel like a student. I’m still learning. I’m one of those fish that just keeps swimming.”