Princess Olympia of Greece celebrated her 21st birthday with an incredibly lavish party in the Cotswolds, attended by aristocracy, celebrities, and royalty -- take a look inside

CakeInstagram/eugeniagaravanniThe Princess’ giant 21st birthday cake was suitably opulent.

Princess Olympia, the eldest daughter of Pavlos, Crown Prince of Greece and Marie-Chantal, Crown Princess of Greece, just celebrated her upcoming 21st birthday in insane style.

The family threw a extremely lavish bash on Saturday in Farmington, Gloucestershire, in the exclusive Cotswolds countryside. The celebration marked the “coming of age” for the Princess, as well as the Prince’s 50th birthday which took place in May.

Naturally, it was attended by hoards of aristocracy and royalty.

The dress code was to “revolutionise your black tie,” and fortunately the guests did not disappoint. They shared their experiences at the party using the hashtag #5021revolution on Instagram.

Scroll down for a sneak peak inside one of the most exclusive and extravagant high society parties of the year.

Princess Olympia, the eldest daughter of Pavlos, Crown Prince of Greece and Marie-Chantal, Crown Princess of Greece, celebrated her 21st birthday at a bash in the exclusive Cotswolds countryside on Saturday.

She wore a spiky crown adorned with flowers, and a Steven Khalil studded and embellished dress which had a long nude tulle skirt. She finished her edgy look with a pair of platform Gucci trainers.

Guests were instructed to 'revolutionise your black tie.' Here, The Princess poses with her cousin Talita Von Furstenberg (Diane Von Furstenberg's granddaughter).

Von Furstenberg attended with her boyfriend George Fair in tow. She affectionately nicknames the Princess 'Limps.'

Heiresses Nikki and Paris Hilton were among the celebrity guests at the party...

...As was model and party girl Poppy Delevingne.

Here, Delevingne poses with the birthday girl and some glamorous pals.

Her father, property magnate Charles Delevingne, also made the guest list.

Proud mother Marie Chantal -- the Crown Princess of Greece -- celebrated with her well-connected circle of friends including art insurer Cyril Karaoglan, Long Island aristocrat Brooke Metcalfe, world-renowned florist Eric Buterbaugh, and publisher Beatrice Vincenzini.

Marie Chantal is the founder of a luxury childrenswear brand.

Pavlos, Crown Prince of Greece, gave a heartfelt speech to mark his daughter's coming of age.

Felipe VI, the King of Spain, even made an appearance at the royal bash.

The rather decadent sweet buffet included macarons and profiterole towers, which resembled something from a medieval banquet.

Princess Olympia's pink 21st birthday cake was suitably opulent.

There was also a better-than-average photo booth, which had life-size statues of lions among its props. The printed snaps read: 'Prince and the Revolution.'

The guests' outfits were just a lavish as the birthday girl's. They were all encouraged to use the hashtag #5021revolution when sharing their photos.

They were encouraged to wear flamboyant headgear, led by Marie Chantal.

Here are more fabulous headdresses.

The dance floor also didn't disappoint.

Marie Chantal was snapped on the dance floor by her friends.

There was a lot of glitter involved.

There were also lots of disco balls.

And, apparently, giant pink inflatable ones, as well.

The party has been called 'epic' by guests -- and we can certainly see why.

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