President Ronald Reagan and his wife Nancy hosted a White House gala dinner for Prince Charles and Princess Diana that fell at the close of their first day in the U.S. While it wasn't a state visit, Americans followed the royals' every move with more intrigue than if 12 world leaders had been in attendance. The adoration started the moment they arrived — some 4,000 oglers went to watch their plane land at the airport. Yet the lasting image from the couple's visit isn't of Charles and Di. Rather, it's of the Princess, wearing a midnight blue velvet gown and sapphire and diamond choker, gliding and twirling across the White House dance floor with movie star John Travolta.