As usual, the fashion predictions came rolling in ahead of the October 20 state banquet at Windsor Castle in honor of the sultan of Oman. When Princess Kate arrived at the official welcome ceremony on Tuesday morning, she wore a head-to-toe green outfit in tribute of one of the colors of the Omani flag. With the rest of the flag made up of red and white, royal watchers were largely expecting a gown—most likely a repeat—in one of those shades. But I can assure you, pale yellow leopard print was not floating around in my mind this evening.

The Princess of Wales arrived at Windsor Castle in a flowing Elie Saab dress featuring a dramatic cape and braided detail along the neckline, and at first glance, the pastel gown is standard royal fare.…