WHEN Terence Conran, designer, restaurateur, businessman, sold off the management of his restaurant group three years ago, it seemed that the sun had set on his culinary empire. Those revolutionary temples to design and gastronomic sophistication that dominated theLondon dining scene in the 1980s and ’90s — Bluebird, Quaglino’s, La Pont de la Tour — were being put in other hands. And when he announced last year...