Queen's Diplomatic Reception at Buckingham Palace on December 5, 2017 in London, England.

Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, who are expecting their third child, were decked out in all their finery for the Queen's Diplomatic Reception at Buckingham Palace on December 5, 2017

Catherine, Duchess of Cambridge wore the Lover's Knot tiara which she is accustom to wear on ceremonial occasions such as tonight's reception at Buckingham Palace

Catherine, Duchess of Cambridge appeared to be wearing a white silk gown which featured intricate embellishment around the neckline off-set by an elegant diamond necklace, during Diplomatic Reception at Buckingham Palace

Camilla, Duchess of Cornwall was joined by Prince Charles of Wales, who too was dressed in all of his finery including several ceremonial medals for the Diplomatic Reception at Buckingham Palace on 5 December 2017

Camilla, Duchess of Cornwall, stunned in a white lace gown which was paired a four-string pearl necklace fixed with a diamond clasp, and she top off with glittering Boucheron tiara that once belonged to the Queen Mother. The Duchess of Cornwall is also wearing The Royal Family Order of Queen Elizabeth II, an honor bestowed on female members of the British Royal Family by the monarch and worn on formal occasions, during Diplomatic Reception at Buckingham Palace.

Prince William, Duke of Cambridge looked his dapper best in white tie, attended the Diplomatic Reception at Buckingham Palace

Catherine, Duchess of Cambridge seen wearing glittering head piece the Lover's Knot tiara. She appeared to be wearing a white silk gown which featured intricate embellishment around the neckline off-set by an elegant diamond necklace. She swept her brunette locks up into a low chignon revealing a pair of pearl drop earrings. As she made the short trip from Kensington Palace to Buckingham Palace for the annual celebratory dinner.

Camilla, Duchess of Cornwall stunned in a white lace gown which was paired a four-string pearl necklace fixed with a diamond clasp and opt for glittering Boucheron tiara that once belonged to the Queen Mother as she attend the Queen's Diplomatic Reception at Buckingham Palace on December 5, 2017

Camilla, Duchess of Cornwall stunned in a white lace gown which was paired a four-string pearl necklace fixed with a diamond clasp. She was pictured wearing the Boucheron tiara, a piece from the Queen's collection most famously worn by the Queen Mother that The Duchess of Cornwall favours when it comes to choosing a tiara. She also wearing The Royal Family Order of Queen Elizabeth II, an honour bestowed on female members of the British Royal Family by the monarch and worn on formal occasions.

Camilla, Duchess of Cornwall was joined by Prince Charles of Wales, who too was dressed in all of his finery including several ceremonial medals for the reception.

Camilla, Duchess of Cornwall and Prince Charles, Prince of Wales depart after attending the annual Diplomatic Reception at Buckingham Palace on December 5, 2017 in London, England.

Prince Charles, Prince of Wales departs after attending the annual Diplomatic Reception at Buckingham Palace on December 5, 2017 in London, England.