Royals from several European monarchies were among the guests, including four future queens - The Netherlands' Princess Catharina-Amalia, Sweden's Princess Estelle, Norway's Princess Ingrid Alexandra and Belgium's Princess Elisabeth.
A number of young royals have celebrated their 18th birthdays in recent years, take a look back at the heirs on their milestones below…
The Prince of Wales
Prince William was photographed in the grounds of Eton College for his 18th birthday snaps in June 2000.
A huge party was held at Windsor Castle that summer to celebrate a number of big royal birthdays – the Queen Mother's 100th, Princess Margaret's 70th, Princess Anne's 50th and Prince Andrew's 40th.
But reports at the time said that William missed out on the bash as he was studying for his A-Level exams.
Crown Princess Victoria of Sweden
King Carl XVI Gustaf and Queen Silvia's eldest child marked her 18th birthday with her first public speech at the Royal Palace of Stockholm.
The Crown Princess wore a royal blue gown and a pearl necklace for the occasion.
She also displayed the Order of the Seraphim on a sash for the very first time.
Victoria married fitness instructor Daniel Westling in 2010, and the pair have two children – Princess Estelle and Prince Oscar.
Princess Elisabeth of Belgium
King Philippe and Queen Mathilde's eldest child commemorated her milestone birthday with a celebration at the royal palace in Brussels.
Politicians, relatives and young people who were born in Elisabeth's 2001 birth year were all in attendance.
Queen Mathilde was visibly emotional as her daughter delivered a moving public speech.
The princess, who is now studying at Lincoln College at Oxford University, was invested with the Order of Leopold on her 18th birthday.
Princess Catharina-Amalia of The Netherlands
The Dutch royal palace released a series of portraits to mark Princess Catharina-Amalia's 18th birthday in December 2021.
The princess was pictured wearing a red belted dress at the royal family's home, Huis ten Bosch, in the Hague.
On that day, King Willem-Alexander also appointed his daughter a Knight Grand Cross in the Order of the Netherlands Lion and a Knight in the House Order of the Golden Lion of Nassau.
Catharina-Amalia has been studying for a degree in Politics, Psychology, Law and Economics at the University of Amsterdam since September 2022.
Princess Ingrid Alexandra of Norway
Around 200 guests attended a banquet at the royal palace in Oslo to mark Princess Ingrid Alexandra's 18th birthday in 2022.
Crown Prince Haakon and Crown Princess Mette-Marit's daughter had her first tiara moment, teaming her deep purple Albert Ferretti gown with the Boucheron Circlet Pearl Tiara - which was made for her great-great-grandmother Princess Ingeborg of Sweden.
Princess Ingrid Alexandra currently has a role as school assistant and environmental worker at Uranienborg School. In 2024, the princess will begin her first year of military training at the Engineer Battalion in Brigade Nord.
Prince Guillaume of Luxembourg
In 1999, Prince Guillaume celebrated his 18th birthday with his family, including his late grandparents, Grand Duke Jean and Grand Duchess Josephine-Charlotte.
Guillaume has been the heir apparent to the crown of Luxembourg since his father's accession in 2000.
He married Stephanie de Lannoy in 2012, and the pair are now parents to Prince Charles and Prince Francois, born in 2020 and 2023 respectively.
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