Princess Martha Louise, along with her now ex-husband Ari Behn, attended the various celebrations for King Carl XVI Gustaf's 70th birthday on behalf of the Norwegian Royal Family. 

For His Majesty's actual birthday on April 30, the King and Royal Family traditionally stands outside Stockholm Palace for the Swedish Armed Forces Celebration. King Carl XVI Gustaf also receives flowers from Swedish children who wish him a happy birthday. 

Princess Martha Louise attended the celebration and the lunch on this day in a MagMaLou dress with gold and black with a feathery fascinator in light pink. The dress also featured a thin belt around the waist. 

Besides Martha Louise and Ari, other European royals traveled to the Scandinavian country for the festivities. Queen Mathilde and King Philippe of Belgium, King Juan Carlos and Queen Sofia of Spain, Crown Prince Frederik, Crown Princess Mary, Princess Benedikte, and Queen Margrethe of Denmark, Princess Beatrix of the Netherlands, Hereditary Prince Alois and Hereditary Princess Sophie of Liechtenstein, Prince Albert of Monaco, and Princess Takamado of Japan were all there to celebrate with the King. 

Many defunct royal families were also represented. 

Princess Benedikte and Queen Margrethe are 1st cousins to King Carl XVI Gustaf, and Crown Prince Frederik is his 1st cousin once removed. 

You can read about her outfit at the banquet here.