By Rita Kokshanian
Updated Dec 08, 2015 @ 5:30 pm
Credit: Mark Cuthbert/UK Press via Getty Images

It's not often Kate Middleton wears a tiara. In fact, the Duchess of Cambridge has worn the royal accoutrement only three times in the past four-and-a-half years (once very recently in October), making it very rare indeed to see one on her head. However, tonight marked a special occasion, because Middleton chose to wear a tiara for the only the fourth time ever—and this wasn't just any ordinary diamond-encrusted topper.

For the Diplomatic Reception at Buckingham Palace, Her Royal Highness wore a tiara that was given to Prince William's late mother, Princess Diana, by Queen Elizabeth II on her wedding day to Prince Charles. Called the Cambridge Lovers Knot Tiara, it was worn by the Princess of Wales many times and consists of 19 diamond frames with a large pearl drop in each—talk about glitzy.

Middleton was snapped en route to the event alongside Prince William, and although we can't see the rest of her outfit yet, it's safe to say that nothing can outshine her gorgeous diamond-and-pearl topper.