Princess Diana's 'priceless' wedding tiara exhibited for the first time in decades

Over the centuries, the tiara, something of a little sister to the omnipotent symbol of the crown, has come to represent more than just a membership to the monarchy. Closely connected to the romantic idea of a princess, it's a cultural shorthand for youth and femininity -- as well as status. From the plastic Cinderella tiaras worn by the millions of children that visit Disney theme parks each year, to the most recent Met Gala -- where multiple celebrities, including Blake Lively and even Anna Wintour herself, wore jewel-encrusted versions -- the ancient accessory continues to be relevant today.

This summer, auction house Sotheby's will display some of history's most influential tiaras -- many which have not been seen by the public in decades -- in a new exhibition called "Power & Image: Royal & Aristocratic Tiaras." The event, which opens in London on May 28, is a celebratory retrospective of 50 tiaras, dedicated to the Queen's Platinum Jubilee -- marking 70 years since the British monarch took the throne in 1952.

Included in the lineup is The Spencer Tiara, famously worn by Princess Diana during her wedding to Prince Charles at St. Paul's Cathedral -- a royal union watched by more than 750 million people across 74 countries. The garland-style tiara, which has a central heart-shape piece and is set with diamonds, has been loaned to Sotheby's London by Lord Spencer, Diana's younger brother, and will be showcased for the first time since the 1960s, according to the auction house. It was a go-to accessory for Diana, who reportedly wore the piece seven times between her marriage in 1981 and her death in 1997.

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It was likely handed down to Diana by her grandmother, Lady Cynthia Hamilton, who received the tiara as a wedding present in 1919. The family heirloom was thought to be first forged in 1767, where it may have looked different to the version worn by Diana on her wedding day. Between 1919 and 1930 the accessory is believed to have been added to and altered, although none of the augmentations were officially recorded. According to the auction house, many tiaras similar to the one belonging to the Spencer family began as brooches or modest headbands -- with decades of jewelers expanding the piece by adding more stones.

And it is, according to Kristian Spofforth, Head of Jewelry at Sotheby's London, genuinely priceless. "It's one of those (items) that is impossible to value," he said in a phone interview. "Given the public interest in Diana, there is absolutely no way we could park a figure on it. It's one of those few objects that you could say is in a way priceless."

Alongside The Spencer Tiara, the exhibit will show one of Queen Victoria's favourite pieces -- an emerald and diamond crown gifted to her by Prince Albert when she was 26 years old. Constructed in a Gothic Revival style, the piece consists of 19 oval-shaped emeralds weighing up to 15 carats.

"The Queen's Jubilee celebrations have given us the perfect opportunity to put on public display an outstanding selection of tiaras from noble and royal provenance," said Spofforth, in a press statement. "This is also a wonderful moment for us to shine a special light on the dazzling craftsmanship delivered by generations of mainly British-based jewellers across several centuries of tiara making."