Surprise, surprise! Diana was wearing illusion lace panels long before they became a wardrobe staple. With strict rules on fashion etiquette as a member of the royal family, Diana wasn't known for showing much skin during her marriage to Prince Charles. But by choosing styles like this Jan van Velden evening gown from 1984, where sheer lace overlays gave the illusion of more coverage, she could play around with sweetheart necklines and more modern silhouettes. It's a trick the Duchess of Cambridge knows all too well: her wedding dress used a similar trick.