While fashion is always changing, certain pairings are generally frowned upon, like wearing socks with sandals. But fashion is one thing, and style is another, and Kate Middleton fans are swooning over her latest sartorial choice that flies in the face of one of fashion’s biggest rules.

It’s been a confusing few months for anyone obliged to write about Kate Middleton ’s wardrobe for a living. First, there was a not-quite announcement, through a source quoted in The Times, that the Palace would no longer be issuing details on the Princess of Wales’s outfits.

For years, Kate Middleton’s fashion choices have been a masterclass in polished, princess-perfect style. But her look on March 15 at the Six Nations match in Cardiff? A quiet departure from the norm—one that signals a shift in how she’s approaching fashion altogether.