You've probably never heard of Princess Antonia, the Duchess of Wellington who just stole the show in King Charles III's company

There were three striking crowns in the room when King Charles III attended the State Opening of Parliament on Wednesday, a number that surprised many royal watchers.

His Majesty wore the Imperial State Crown; Queen Camilla wore the State Diadem, one of the most recognisable pieces of the crown jewels; and the little-known Duchess of Wellington wore her own headpiece that almost stole the show.

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She arrived at the House of Lords dripping in white lace and diamonds, one of the Wellington family's most beautiful tiaras perched atop her head.

Photos of the duchess waiting for the ceremony to start quickly raised eyebrows, with many a royal watcher wondering just who she was and how she earned an invitation to the event.

Born Princess Antonia Elizabeth Brigid Louise Mansfeld of Prussia on April 28, 1955, she was a royal from her first moments in the world.

Her father was Prince Frederick of Prussia, grandson to the German Emperor Wilhelm II, and her mother was Lady Brigid Guinness, who was herself the daughter of an earl.

Antonia is also great-great-great-granddaughter to Britain's Queen Victoria and has a twin brother named Rupert.

Though her great-grandfather Wilhelm II was ousted as the last Kaiser (Emperor) of Germany after the revolution of 1918, Antonia enjoyed all the benefits of an aristocratic upbringing.

She was sent to private schools, educated at King's College London, and earned herself another title when she married Charles Wellesley, Marquess of Douro in 1977.

Then-Prince Charles was among the notable guests at their wedding, and the Queen Mother, Princess Margaret, and the Duke and Duchess of Kent also attended.

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Antonia welcomed five children with her husband, two sons, Arthur (born 1978) and Frederick (born 1992), and three daughters, Honour (born 1979), Mary (born 1986) and Charlotte (born 1990). All are lords and ladies.

When her husband became the 9th Duke of Wellington following his father's death in 2014, Antonia also gained a slew of new titles and peerages.

She became the Princess of Waterloo in Belgium and the Netherlands, the Duchess of Victoria in Portugal, the Duchess of Wellington in the UK, and the Duchess of Ciudad Rodrigo in Spain.

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As well as her many titles, the princess was appointed an Officer of the Order of the British Empire in 2008 and has been close with the royal family for decades.

She attended King Charles III's coronation in 2023, where her husband bore Queen Mary's Crown in the royal procession, and she even accompanied the King and Queen to Royal Ascot that year.

The Duchess of Wellington was also invited to His Majesty's first State Opening of Parliament as monarch last year, which she attended in another stunning tiara.

That sparkling diamond headpiece dates back to the 19th century and has been in her husband's family for decades, having originally belonged to the second Duchess of Wellington, Lady Elizabeth Hay.

The same is likely true of the tiara Antonia chose for her latest outing, another glittering piece said to date back to the 1850s.

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