Attending a wedding rehearsal ahead of their big day, the pair couldn't have looked more thrilled at the prospect of making their relationship official
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Nikolaos' parents King Constantine and Queen Anne-Marie also look delighted
Spetses, three hours away from Athens, has the honour of hosting the nuptials
When Crown Prince Pavlos of Greece wed his American heiress wife Marie-Chantal in 1995, his father King Constantine said: "It's very difficult for a father to give away his daughter, but I believe that (she) is in good hands with a good family.
"Not because Pavlos is my son but because he is really a nice boy".
As the Greek royals gather some 15 years later to see another 'nice boy' - the crown prince's 40-year-old brother Nikolaos - marry his sweetheart Tatiana Blatnik, his sentiments must be the same.
London-based Nikolaos, a graduate of Brown University in the US, who currently works in his father's office, appeared openly emotional at the solemn step he is about to take.
His excitement was mirrored by his beautiful fiancée's.
Her right hand clasped in his, a megawatt smile on her face, Tatiana, 29 - an events planner for Diane von Furstenberg - already looked like the radiant bride she is sure to be on Wednesday, August 25.
Around 350 distinguished guests representing Europe's most blue-blooded families will be welcomed to the island of Spetses, which is three hours away from Athens, by the king and his wife Queen Anne-Marie, along with their five children.
It is not strictly a royal wedding since King Constantine was deposed in 1974 – but royal protocol is being followed by attendees.
The mother of the bride, for example, was seen bobbing a curtsey, as she greeted the queen, as well as giving her a kiss.
On her marriage her daughter will be styled HRH Princess Nikolaos of Greece and Denmark – Constantine is descended from the northern European country's Christian IX, allowing his family to use that title.
For the ceremony in the picturesque monastery of Ayios Nikolaos Tatiana will arrive in a horse-drawn carriage.
Meanwhile, groom is expected to arrive in dashing style. Escorted by police and coast guards, he will take a boat, from the nearby town or Porto Heli, to end his bachelor days.