From left: Prince Harry, Kate and Prince William
The Duchess of Cambridge
was looking good
for Her Majesty on Friday.
She joined husband William
and his brother Prince Harry
for a special lunch at Windsor Castle during which Queen Elizabeth entertained monarchs from 26 countries and most members of her immediate family.
Kate, 30, wore a $2,000 coat dress designed by Emilia Wickstead. Described as a pleated dress with a square neck, it is made of double crepe wool and is from the current collection.
The stylish Kate
was seen chatting with William
, 29, and Harry, 27, in the Waterloo Chamber at the Castle before a lunch of English asparagus tartlet, new season Windsor Lamb with braised potatoes and vegetables – and a tomato and basil salad.
Dessert was strawberries and vanilla charlotte.
Guests included Prince Albert and his wife Charlene
; the former king of Greece; the kings and queens of Denmark, Norway and Sweden; and King Abdullah and Queen Rania of Jordan.
Among the younger British royals: Princesses Beatrice and Eugenie
, who attended with their father Prince Andrew. Later, Prince Charles
and his wife Camilla are hosting a dinner for the visiting sovereigns back in London at Buckingham Palace.
For more on Kate's sexy style, pick up the latest issue of PEOPLE, on newsstands now