As Prince William and Princess Kate prepare themselves for a future on the throne , their royal roles have become more important than ever. When the Royal Family welcomed Sultan Haitham bin Tariq Al Said of Oman for an official state visit on October 20, the Princess of Wales showed how soft diplomacy is done—and one royal biographer says that her upbringing plays a “key” role.

Wearing a floaty new Elie Saab gown with her go-to Lover’s Knot Tiara , Kate not only brought royal glamour to the state banquet on October 20, but she helped Windsor Castle ’s guests feel at home.

"Catherine gets it right every time—she’s always on her A-game,” royal biographer and journalist Robert Jobson told Hello! magazine .…