The couple's upcoming nuptials will be incredibly intimate, with reports suggesting that just 60 people will be in attendance. As such, their wedding dinner featured a slimmed down guests list of their family members, including Queen Anne-Marie and Queen Sofia of Spain. Princess Theodora and husband Matthew Kumar also made a rare joint appearance for the meal.
The future groom and bride to be smiled as they were seen arriving, while other members of the family arrived in separate cars.
See the best photos from the event below…
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Nikolaos and Chrysí arrive
Nikolaos and Chrysí were a picture of love as they smiled and laughed with each other while arriving for the intimate gathering.
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The couple's outfits
The next time we see the pair, they'll likely be in their stunning wedding outfits. For this event, Nikolaos wore a sleek blue suit, while Chrysí wore black trousers and a checkered coat.
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Anne-Marie's arrival
The mother of the groom looked radiant as she arrived at the event. The former Queen of Greece looked opulent in her coat and earrings.
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Royal accessories
The 78-year-old carried a gleaming clutch bag with her as she stepped out of her car. Princess Theodora and her new husband, Matthew Kumar, joined her for the journey.
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Princess Theodora
Theodora had joined her mother at the previous day's rehearsal dinner. For Wednesday, Anne-Marie wrapped up in a beige coat while Theodora wore a black coat with a floral dress.
The former Queen of Spain, Sofia, is the groom's aunt, and she looked delighted to join her nephew.
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Prince Constantine-Alexios
Constantine-Alexios looked incredibly dashing as he stepped out to support his uncle.
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Nikolaos and Chrysí leave
The happy bride and groom-to-be were the last to leave their party, beaming at the cameras who had gathered outside the restaurant.
The Greek royals – five surprising facts
Before becoming monarch, the late King Constantine II was an Olympic sailor. He won a gold medal in the Dragon event at the 1960 Olympics, alongside Odysseus Eskidioglou and Georgios Zaimis.
It's not just in sports where the family excels, as both Princess Theodora and Prince Achileas-Andreas are professional actors, and both have had roles in American soap opera The Bold and the Beautiful.
The family has links with other royal houses in Europe. Queen Anne-Marie is descended from the Danish royal family. Meanwhile, Constantine's younger sister, Sofia, became the Queen of Spain.
Princess Alexia had to delay her 1999 wedding to Carlos Morales after the pair were injured in a sailing accident before the big day.
The British royals were incredibly close with the Greek royals. The late King Constantine was one of Prince William's godfathers. Meanwhile, the Prince of Wales is a godfather to Prince Constantine-Alexios.