It's a very rare tiara night for Kate Middleton in London. The Duchess of Cambridge was photographed en route to the Queen's annual Diplomatic Corps Reception. She is wearing the Cambridge Lover's Knot tiara with diamond dangle earrings and what appears to be a navy gown by Alexander McQueen.

Kate Middleton
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Last year, photographers were allowed inside the event to take photos of the guests and their full outfits. Kate wore the Cambridge Lover's Knot tiara then with a Cinderella-esque light blue Jenny Packham gown. It's not clear at this point whether or not the same thing will happen this year, but traditionally access is restricted, and it's treated like a private event. Car shots of royals arriving at Buckingham Palace are all photographers get.

The Duke & Duchess Of Cambridge Attend Evening Reception For Members of the Diplomatic Corps
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Kate at the reception last year.

Kate last wore a tiara in June this year, during the state banquet the Queen threw for President Donald Trump during his state visit. Kate chose the Cambridge Lover's Knot tiara again, pairing it with the Queen Mother's sapphire diamond earrings.

Why isn't Meghan Markle having her first tiara moment tonight? The Duchess of Sussex and her husband Prince Harry are on leave from royal duties this holiday for extended family time. The couple will also spend Christmas away from the royal family.

Their spokesperson announced last month that "the Duke and Duchess of Sussex are looking forward to extended family time towards the end of this month. Having spent the last two Christmases at Sandringham, Their Royal Highnesses will spend the holiday this year, as a new family, with the Duchess’ mother Doria Ragland. This decision is in line with precedent set previously by other members of the Royal Family, and has the support of Her Majesty The Queen."