When the princess of wales arrived at the Royal Albert Hall to attend the Festival of Remembrance on Saturday evening, her outfit followed a now well-established formula for the particularly somber occasion in the royal calendar: a demure black coat dress, sentimental jewelry (in this case, Diana, Princess of Wales Collingwood earrings earrings), “relevant” jewelry (in the form of a Monica Vinader necklace) and ambitious decoration (a classic mini flap bag from Chanel). And come Sunday morning? She was back in another black coat dress, this time by Catherine Walker, to appear at the Cenotaph, a trio of poppies attached to her lapel and the late queen’s dangling Bahraini pearl earrings in her ears.

LONDON, ENGLAND – NOVEMBER 22: Catherine, Duchess of Cambridge attends the Place2Be Wellbeing in Schools Awards at Mansion House on November 22, 2016 in London, United Kingdom. (Photo by Karwai Tang/WireImage)

Getty Images

Both looks were classic Kate and entirely appropriate for a weekend dedicated to honoring those who have lost their lives in service — and yet they still felt, somehow, unusual, given how it is rare to see Windsor women in black. It has often been reported that, with the exception of November’s Remembrance weekend, members of the royal family are prohibited from wearing these glasses from head to toe, except in cases of mourning, when their crepe and sails are traditionally associated with beads. As is often the case with Buckingham Palace protocol, however, there have been exceptions over the years, as members of the royal family decide to let loose momentarily.