Fall's runways were awash with would-be English aristo-eccentrics, but the real thing is increasingly rare. One stellar example: Deborah, the duchess of Devonshire. At 83, she still has the telltale ramrod posture, English rose complexion, and, of course, the dog hairs on her Scottish cashmeres. Youngest of the six famous (often notorious) Mitford sisters, Debo's marriage to the 11th Duke of Devonshire put her squarely into the social whirl, and for a few years she gamely did the cocktails-and-ball-gown circuit. But her heart lay more with family, farm, and the demands of Chatsworth, her husband's grand ancestral estate, where she knocks about the legendary gardens and stables in a Balmain couture raincoat and, often, in the company of her granddaughter, the lanky supermodel Stella Tennant. Must be something in the genes.