Queen Margrethe bestowed her daughter a great new honour.
Mary has been appointed to Denmark's Council of State.
Effective immediately, Mary is now able to attend to the Queen’s duties as head of state when her mother-in-law and husband are abroad.
Crown Prince Frederik, his brother Prince Joachim and the Queen's sister, Princess Benedikte are the only other members of the family to hold this honour.
With both Mary and Charles moving up in their respective royal families, there's no doubt they will have had a lot in common to talk about during the event.
Mary and Fred aren't the only royals to support Emperor Naruhito.
Europe's biggest royals including Prince Charles, Queen Maxima of the Netherlands and her husband, King Willem-Alexander, all attended the large banquet in Tokyo - which was held by the Japanese Prime Minister - in order to celebrate the newly throned Emperor Naruhito.
Last year, the 71-year-old admitted for the first time that she had a deep fear of flying when the Royal appeared on ITV's This Morning.
Her phobia has meant the Duchess often will miss royal engagements with Prince Charles and has led to her cutting her overseas trips short in the past, including the couple's visit to Australia in April 2018.