Princess Lilian's Remarkable Royal Stag Brooch

This royal jewelry commission challenged the talented artisans at Cartier, who were supervised by the brother-in-law of a controversial princess

Eighty-four years ago this month, an imprisoned monarch secretly married a beautiful young commoner, raising eyebrows across Europe—and ensuring a happy future for himself in the process. Today, we examine a royal jewel made as a tribute to their love story.

The Princess of Réthy's Stag Brooch is displayed as part of the Cartier exhibition at the Victoria & Albert Museum in London, April 2025 (© Lauren Kiehna)

Inside the special rooms housing the Cartier exhibition at the Victoria & Albert Museum in London, a stark white wall surrounds a tiny piece of royal jewelry. The bauble is a brooch, made to resemble the head of a stag, encrusted in diamonds, rubies, and emeralds. While many other brooches worn by queens, princesses, and duchesses are featured in the exhibition, this unusual little brooch is given a place of honor, partly because of the woman who wore it and her connection to the Cartier family.

The Princess of Réthy, born Mary Lilian Baels, was the owner of the diamond stag. As the second wife of the widowed King Leopold III of Belgium, she endured a storm of opposition from those who were firmly committed to the memory of his first wife, the late Queen Astrid, as well as from others who were concerned about the irregular way that Leopold and Lilian’s marriage was contracted. The relationship wasn’t the reason that Leopold was eventually compelled to abdicate, but it certainly didn’t improve his public reputation in certain circles ahead of that decision.

Regardless, Lilian would remain married to the former monarch for the rest of his life, adding three more children to his family and creating a glamorous world on the royal periphery with him in Belgium and Switzerland. The stag brooch was a testament to the longevity of their relationship. But, like so many royal jewels, we can’t begin to tell the story of the brooch without first looking back on Leopold and Lilian’s unusual pair of royal weddings in 1941.

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On September 11, 1941, Cardinal Jozef-Ernest van Roey, the Archbishop of Mechelen, arrived at the Palace of Laeken on the outskirts of Brussels. Cardinal van Roey had been summoned to the palace to visit King Leopold III, but not for a standard royal audience. The King had been held as as a prisoner of war inside the castle by the Germans for more than a year. With him there were his three children, Princess Joséphine-Charlotte, Prince Baudouin, and Prince Albert, and his mother, Queen Elisabeth.

Now, a new person was being added to the family. Cardinal van Roey had been asked to come to the palace to perform a wedding. King Leopold had been widowed in 1935 when his wife, 29-year-old Queen Astrid, was killed in a car accident in Switzerland. Leopold, who was then 34, had only been on the throne for a year when his wife died, leaving him to face the burdens of kingship and the challenge of raising three young children alone. Six years later, with his fortieth birthday on the horizon, Leopold was ready to marry again, even amid his perilous political situation.