Earlier this week, Kate Middleton and Prince William welcomed Ukrainian President Volodymyr Zelensky and First Lady Olena Zelenska to Buckingham Palace (opens in new tab) for their first royal engagement since the blockade began. Kate wore a cornflower blue Emilia Wickstead midi dress and striking sapphire and diamond jewelry for the occasion. Princess Diana's engagement ring has been seen before, and the earrings are familiar to royal style trackers, having been refashioned from Princess Diana's. However, Kate finished the set with a matching sapphire and diamond pendant connected to a fine gold chain.

As "People" reports (opens in new tab), the necklace likely originally belonged to the same jewelry set as Kate's earrings, albeit in a different form; in 1981, the Saudi royal family gave Princess Diana an engagement ring ( which also later became Kate's) with a full set of sapphire and diamond jewelry designed to match; according to People, the full set included "a huge Burmese sapphire and diamond pendant suspended from a thin diamond necklace," "matching earrings ring, bracelet, and watch."

In the photo below, taken in Brisbane, Australia, in 1983, Diana is wearing several of them.

Since the Duchess of Cambridge had previously refashioned her late mother-in-law's jewelry, it seems safe to say that Kate's new necklace was a wedding gift for Diana (the pendant matches the earrings perfectly). Mystery solved.