Princess Margaret wears the tiara during the celebrations for the inauguration of Queen Juliana of the Netherlands, 6 Sep 1948 (Dutch National Archives/Wikimedia Commons)

When the Duchess of Sussex unearthed Queen Mary’s Diamond Bandeau for her wedding earlier this year, royal jewel lovers rejoiced. But get excited, because there is very likely another diamond bandeau from Mary’s collection still extant in the vaults: her Diamond Lozenge Tiara.

Queen Mary acquired the tiara — a low, sleek kokoshnik-shaped tiara made of diamonds set in a lozenge pattern and topped with 13 pearls — sometime before 1935. That December, she wore the tiara for her very first film premiere appearance. She attended the debut of The Ghost Goes West in Leicester Square alongside the Duchess of Kent on December 17, still clad in deepest mourning following the death of her sister-in-law, Princess Victoria.

You’ll also often see a photograph of Mary wearing the tiara with a white fur. That image was taken four years later, when Mary attended a performance by the Comédie-Française at the Savoy Theatre on March 1, 1939. On that occasion, she was accompanied by the French ambassador, Monsieur Corbin, and Lady Bessborough.

Princess Margaret wears the tiara during the celebrations for the inauguration of Queen Juliana of the Netherlands, 6 Sep 1948 (Dutch National Archives/Wikimedia Commons)

A decade later, Mary loaned the tiara (sans its pearl toppers) to her granddaughter, Princess Margaret. The princess, who had just turned 18, was headed to the Netherlands for the inauguration of Queen Juliana. (By tradition, monarchs don’t attend each others’ coronations/inaugurations, sending their heirs instead. Margaret attended because her sister, the future Queen Elizabeth II, was pregnant with her first child, Prince Charles.)

Accompanied by the Earl and Countess of Athone (who was a cousin of Juliana), Margaret packed the Cartier Halo Tiara and the Diamond Lozenge Tiara in her luggage as she headed to Amsterdam. It was Margaret’s first trip to the continent and her first official engagement outside Britain.

Princess Margaret wears the tiara during the celebrations for the inauguration of Queen Juliana of the Netherlands, 6 Sep 1948 (Dutch National Archives/Wikimedia Commons)

Margaret, who was ranked fourth in precedence among the royal guests, paired the Diamond Lozenge Tiara with pearls for a “sports fantasy” showcase at Amsterdam’s Olympic Stadium following the inauguration. (She chose the Halo Tiara for a concert held the following evening.)

This tiara hasn’t been seen in public for a little more than half a century, but I have significant hope that this petite sparkler still resides in the royal vaults today. Here’s hoping we see one of the younger princesses take this tiara out for a spin soon!

Image licensed to The Court Jeweller; do not reproduce

The tiaras that Queen Elizabeth II has worn throughout her lengthy reign have all come from the royal vaults — with one very interesting exception. Today, we’re talking about the Plunket Tiara, a piece which unexpectedly came to HM’s rescue one night in early 1973.

Image licensed to The Court Jeweller; do not reproduce

On January 3, 1973, the Queen helped ring in a new year and a new era for the continent at the “Fanfare for Europe” gala, held at the Royal Opera House in Covent Garden. The event was part of the celebrations marking the Britain’s entry into the Common Market. But on the way to the gala, the Queen, who was dressed to the nines, suffered a rare jewel malfunction when her tiara broke.

Image licensed to The Court Jeweller; do not reproduce

There was no time to return to the palace and retrieve another tiara, but one of the Queen’s courtiers and closest friends came to the rescue. Patrick Plunket, who was both the 7th Baron Plunket and a central member of the royal household, lived nearby, and he was able to run home and grab his family’s diamond tiara for her to wear. The Queen placed it on her head and arrived at the gala as if nothing had happened at all.

This color photograph from the evening shows a bit of the glitter of the Plunket Tiara’s diamonds. The Queen, who was escorted by Prime Minister Edward Heath, didn’t just face tiara problems on her way to the gala; news reports note that she and Heath were booed by protestors as they arrived at the opera house.

Image licensed to The Court Jeweller; do not reproduce

This closer view of the tiara, taken as the Queen swept into the opera house, shows some of the diamond detail of the piece. We know a little about the tiara swap thanks to some clever sleuthing done by Cynthia, a member of the Royal Jewels of the World Message Board. (You can read her original message on the subject here.)

The tiara loan is just one small anecdote from the Queen’s fascinating, lifelong friendship with Lord Plunket. In 1974, she made him a Knight Commander of the Royal Victorian Order (perhaps partly as thanks for the tiara help?). Sadly, Plunket died of cancer in 1975, but even in death, his importance to the Queen was underscored. He was buried in the royal family’s private grounds at Frogmore, and the Queen commissioned an impressive memorial in his honor in Windsor Great Park.

(Oh, and one more tiara-related sidenote re: Lord Plunket. He was an accomplished art collector who had an excellent eye. In 1959, he was the person who found out about the sale of the Poltimore Tiara and advised Princess Margaret to buy it. In the literature from the Christie’s auction of the tiara in 2006, the piece is even referred to as “Patrick’s tiara,” suggesting that Margaret herself called it by that name.)

One question remains, though: which of the Queen’s tiaras was damaged on the way to Covent Garden that night? We don’t know for sure, but thanks to the Queen’s tendency to repeat favorite combinations of gala jewels, we can make a pretty good guess. She also wore the Gloucester Pendant Earrings and Queen Victoria’s Golden Jubilee Necklace for the gala, and the tiara that she usually paired with those jewels in the early 1970s was the mighty Vladimir Tiara.

David Cairns/Daily Express/Hulton Archive/Getty Images

In fact, the Queen wore that exact combination of jewels twice the previous autumn, for state banquets in Yugoslavia (hosted by President Tito on October 20, 1972) and in Britain (where she welcomed President Heinemann of West Germany to Windsor Castle on October 24, 1972).

We also know that the Vlad, which was nearly a century old at this point, was showing its age significantly. It had already been significantly repaired once by Garrard (in 1924, following damage incurred when it was smuggled out of Russia), and in 1988, the frame of the tiara had to be completely rebuilt. I wouldn’t be surprised at all if there were breaks and repairs along the way — including perhaps on this occasion.