<DIV>The archives of British Vogue define modern portraiture. Its collection remains a stylish barometer of the social and cultural changes that shaped the 20th century. From princesses to rock stars, models to actors, society beauties to world leaders, these are portraits of figures who have made an enduring mark on their age. And just as the pictures are a who's who of the brilliant and beautiful, the selection of photographers is equally stellar. Daring, discerning, iconoclastic?here are the people who defined their art, including Horst, Beaton, Steichen, Penn, Snowdon, Parkinson, Bailey, and Testino.</DIV>