Sound the royal alarm: The extended British royal family is now short one priceless piece of headwear. Last week, thieves snatched the Portland Tiara right out of its armored glass display case inside the Welbeck Estate in Nottinghamshire, England, according to the BBC. The robbers reportedly broke into the Portland Collection gallery on the estate's grounds sometime between 9:45 and 10 p.m. on Tuesday, broke the glass case—triggering an alarm—and stole both the historic tiara and a pendant made from diamonds that remained after the tiara was refurbished. "Security services missed the thieves by 90 seconds and the police arrived on the scene two minutes later," a Welbeck Estate spokesman told the BBC.

The elaborate headpiece showcases the large, rectangular Portland Diamond, around which are arranged several smaller diamond pendants, all dangling within crystal-encrusted loops. The tiara was reportedly commissioned from Cartier for Winifred, Duchess of Portland, by her husband, for her to wear to King Edward VII's coronation, in 1902. Richard Edgcumbe, jewelry curator for London's Victoria and Albert Museum, described the Portland Tiara to the BBC as "one of the great historic tiaras of Great Britain." James Lewis, from Bamfords Auctioneers, told the outlet that the piece "could be worth millions," but noted that, since it's such a famous and historic object, rather than attempting to sell the tiara as a whole, the thieves might make the "horrendous" choice to break it apart and sell the diamonds individually.

Welbeck Estate/Nottinghamshire Police

In a Facebook post, the Nottinghamshire Police wrote that they were investigating "a number of lines of inquiry," including one concerning a silver Audi S5 that was found "abandoned and burnt out" near the gallery about 30 minutes after the heist. "We particularly want to hear from anyone who has any information about a silver Audi S5, which is suspected to have been involved in this offense. Did you see this vehicle in the Welbeck area around the time of the burglary or anywhere between the Welbeck Estate and Cross Lane in Blidworth between 9:45 p.m. and 10:30 p.m. on Tuesday night?" Detective Inspector Neil Humphris wrote in the post, adding that the police are also looking for anyone who may have captured "dash cam footage" of the car.

A week after the robbery, neither the jewels nor the owner of the Audi have been tracked down. In the meantime, the Portland Collection space at the Welbeck Estate has remained closed, as the "deeply saddened" gallery announced on its website.

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