Queen Mary has added another tiara to her growing collection, wearing a diamond and sapphire headpiece with links to Russia’s last imperial family and purchased at auction for $500k.

It is the latest example of Queen Mary reworking an heirloom piece to make it her own, something she has done on several occasions since her husband Frederik X ascended the throne as king in 2024.

King Frederik X and Queen Mary of Denmark hosted a state banquet for Vietnam’s visiting presidential couple at Christiansborg Palace on Tuesday. Martin Sylvest Andersen/Getty Images

Queen Mary wore the historic tiara for a state banquet at Christiansborg Palace on Monday evening, held in honour of Vietnam’s visiting president and his wife who are on a three-day visit to Denmark.

King Frederik and Queen Mary were joined by their son and heir Crown Prince Christian, who celebrated his 21st birthday on October 15. Christian wore the gala uniform of the Royal Life Guards and the Grand Commander’s Cross with the star of the Order of the Dannebrog, awarded by his father on his birthday.

But it was Queen Mary’s outfit, and choice of jewellery, which has surprised royal watchers.

Mary, 54, debuted the tiara once known as the Russian sapphire diadem.

It belonged to King Frederik’s great-grandmother Queen Alexandrine and was a wedding gift from Russian Tsar Nicholas II when she married Prince Christian, later known as Christian X, in 1898.

Since then, the jewel has been worn by several generations of the Danish royal family and underwent several redesigns and adaptations in keeping with the changing fashions of the time.

It was sold by the Rosenborg family at auction in 2018 for two million Danish kroner (approx. $445k) to an unknown buyer.

In 2024, the tiara was acquired by the Danish Royal Collection from a private owner.

Queen Mary debuted a newly reworked tiara from the Danish Royal Collection featuring sapphires and diamonds. Martin Sylvest Andersen/Getty Images

Soon after, Queen Mary worked with Copenhagen-based jewellery designers Diana Holstein and Hanan Emquies to give “the piece of jewellery a new, fully reversible design”, the Royal House said.

“A design that respects the piece’s history and special tradition and makes it usable today,” the Royal House said.

The piece can now be worn as a tiara, necklace or brooch, “continuing the historical tradition of royal jewellery being adapted to the needs and tastes of new generations”, it added.

Pinned to a velvet band on Queen Mary’s wrist was the brooch which was previously the central motif attached to the tiara.

Pinned to Queen Mary’s skirt and top by Danish designer Jesper Høvring was the Order of the Elephant. The Danish Royal House

Since Mary became queen in January 2024, she has delved into the vaults to wear pieces that had previously been ignored or worn very little.

In December 2024, Mary wore a new tiara that had been made using stones from the rose-cut diamond set of the Danish Crown Jewels. Aptly named the rose-cut diamond bandeau, the tiara was made with the large stones taken from a diamond belt. Mary chose to have the belt re-fashioned into a tiara that could be worn throughout her husband’s reign.

It was the first time in more than 180 years that the Crown Jewels had been reworked in such a drastic fashion.

The state banquet was held inside the Great Hall at Christiansborg Palace and the floral arrangements chosen to represent the flags of Vietnam and Denmark. Martin Sylvest Andersen/Getty Images

Months later, Mary would surprise again.

During a state visit to Finland in March last year, Queen Mary wore a tiara that had not been seen in public for 140 years. The gold tiara was made in 1820 for Caroline Amalie, who was married to Denmark’s Christian VIII, who reigned from 1839 to 1848.

And in May this year to the 80th birthday celebrations of Sweden’s King Carl XVI Gustaf, Queen Mary wore a diamond bracelet mounted onto a frame allowing it to be worn as a tiara. The jewel once belonged to Sweden’s Queen Lovisa, whose daughter later became Queen Lovisa of Denmark in 1906.

Crown Prince Christian joined his parents for the state banquet just days after celebrating his 21st birthday. The Danish Royal House

For the palace gala this week, the queen wore a favourite outfit by her long-time Danish designer Jesper Høvring which was first seen on Mary in 2014.

The outfit has been worn many times, and in various forms, since then.

In 2022, Høvring told nine.com.au how the outfit had undergone several changes since it was acquired by Mary after seeing it during his catwalk show.

“That is absolutely one of my favourites and one of the dresses that we get the most response to from our clients,” he said.

“They still come with pictures and say, ‘Can we have something like this?’”

Queen Mary also had a leading role in the floral arrangements which decorated the Great Hall, where the state banquet took place.

Queen Mary welcomed Vietnam’s first lady Ngo Phuong at Copenhagen Airport on Monday. Liselotte Sabroe/Ritzau Scanpix via AP

The red and yellow colours of the flowers were chosen to represent the Vietnamese and Danish flags. Guests dined on Greenlandic cod with seaweed, roasted free-range veal  and macaroon cake.

The Danish royals and their family connection to Vietnam

Earlier on Monday, King Frederik and Queen Mary welcomed Vietnam’s president Tô Lâm and his wife, Ngô Phương Ly, to Copenhagen marking the start of the state visit.

The king and queen met the visiting couple at the airport before joining them in a carriage procession to palace square at Amalienborg.

The two couples rode in a carriage through Copenhagen, arriving at Amalienborg marking the beginning of the state visit. Martin Sylvest Andersen/Getty Images

The three-day visit aims to highlight areas of common interest between Denmark and Vietnam including green solutions, health, food, and further regional and international cooperation.

In what was likely a coincidence, Queen Mary and the president’s wife both wore burgundy. Mary flew the flag for local designers, wearing a headband by milliner Katrin Cecilia Jacobsen and a blue checked bouclé dress with a navy silk collar by Lasse Spangenberg.

Then-Crown Prince Frederik and Crown Princess Mary of Denmark visited Hoan Kiem Lake during a business promotion to Hanoi, in November 2022. australscope

In 2022, Frederik and Mary travelled to Hanoi on a business visit as crown prince and crown princess to mark the 50th anniversary of the establishment of diplomatic relations between the two countries.

They spent the majority of their time in Hanoi, a city that has a special connection to the Danish royals. Prince Frederik’s late father Prince Henrik was born in France but spent the first five years of his life in Hanoi which at the time was the capital of French Indochina.

On the eve of the tour, Mary and Frederik were photographed outside the childhood home of Prince Henrik in the bustling city.

Prior to 2022, the couple’s last visit to Vietnam took place in 2009 with Queen Margrethe II and her husband.