Crown Princess Mary attended the dinner with her husband, Crown Prince Frederik of Denmark, and the couple greeted Queen Maxima and her husband, King Willem-Alexander. The two women were matching in elegant black dresses, but their outfits were not the only things to stand out.
Mary and Maxima’s body language with one another was a sight to behold.
When Mary saw the Dutch Queen, she curtsied very low, her knee almost touching the ground.
The Princess has done this before – most notably in 2015, when she curtsied in front of Maxima and put her hands on the Queen’s waist.
But why do this when curtseying is no longer necessary within royal households?
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The Danish royals no longer expect curtseys as it is something that is seen as too formal.
However, despite it not being royal protocol, Mary often curtsies when she sees Queen Maxima.
According to body language expert Judi James, it is a sign of respect between two good friends.
She told Express.co.uk: “Princess Mary’s curtsies to Queen Maxima aren’t just curtsies, they are deep, elegant, sweeping curtsies that make the average knee-bend bob look half-hearted by comparison.
“Mary and Maxima’s body language together has long defined them as friends who enjoy each other’s company as do, apparently, their husbands.
“The men are often seen chuckling at Mary’s emphatic act of lowering to signal respect, but it does seem to be important to her.”
Judi noted: “In reality, Mary combines the curtsey with a mimed hug that leads to the warmest, closest hug when she is back on her feet again.
“As she bends she keeps her gaze up and her hands clasp Maxima’s arms in a way that wouldn’t happen with someone who is not as close.
Meanwhile, Queen Maxima wore a Carolina Herrera midi gown featuring a bateau neck and a black leather belt.
The Dutch royal finished the look with a Gianvito Rossi satin clutch bag and matching heels.
As for jewellery, she donned a pearl necklace with a diamond clasp, diamond stud earrings, and a Patek Philippe watch.
Royal fans were quick to comment on Maxima and Mary’s looks, as well as their friendship.
Instagram user @ellainthecityboston said: “Love seeing these two dynamic women together.”
User @trinidadalarcon67 wrote: “How divine.”
User @salmacg1419 said: “Now that is a curtsy!”
However, some believed the Mary’s curtsy was old-fashioned and “ridiculous”.
User @twinklewrinkle_age commented: “Looks so ridiculous to me.”
Natalia Gonzalez agreed. She said: “Ridiculous.”
User @sammyandhisfamily wrote: “It looks so awkward.”
Janet Geall added: “It’s out of date.”