All About Princess Anne's Hat, 'Feathergate' and Why She Wore a Uniform to King Charles' Coronation

King Charles' coronation on Saturday had much to be excited about. There was the King's robe made of crimson velvet, Princess Charlotte's Alexander McQueen dress and cape, the historic Gold State Coach pulled by eight horses — but on Twitter, it seemed like people only had one thing on their minds: Princess Anne's hat.

In fact, the topic was trending most of the afternoon.

The Princess Royal, who is the only sister of King Charles, performed a very important role during the ceremonies. As Gold-Stick-in-Waiting, she acted as the King's personal protection officer. So she wore military costume, the Uniform of the Blues and Royals, complete with a garter sash and star and full sized medals. But the real star: a triangle-shaped hat with a large, red feather.

Many Twitters said her look exuded strength and power.

"Princess Anne ready to defeat Napoleon should the need arise," said one user, while another commented, "Princess Anne slaying at her brother's coronation."

Others felt the feather stole the show — not an easy task in a room full of diamond headpieces and tiaras.

Jess Cartner-Morley, who writes about fashion for The Guardian, seemed to be re-thinking her view of Princess Anne from the feather.

"Has Princess Anne been the cool one all along?" she tweeted. "She is actually pulling this look off."

Using the hashtag #feathergate, some Twitter users speculated that the feather was placed to block Prince Harry, who sat directly behind his aunt. Indeed for much of the ceremony, it was impossible to see his face from certain camera angles.

The feather also drew comparisons to a candle that obscured Meghan Markle's face at Queen Elizabeth's funeral in September.

Prince Harry, 38, and his aunt appeared to have a happy exchange as Princess Anne entered Westminster Abbey to take her seat. The Duke of Sussex was seen smiling at his relative, decked out in full royal regalia.

Following the crowning ceremony, many members of the royal family participated in the Coronation Procession back to Buckingham Palace by riding in horse-drawn carriages or cars — but Princess Anne was the only royal to ride on horseback in her role as Gold-Stick-in-Waiting.

In an interview with CBC News that aired Monday night, Princess Anne joked about the perks of the job.

"I have a role as the Colonel of the Blues and Royals in the Household Cavalry regiment as Gold Stick [in Waiting]. And Gold Stick was the original close protection officer. So that is a role I was asked if I'd like to do for this coronation, so I said yes," she said. "Not least of all, it solves my dress problem."

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While her older brother may be King, Princess Anne often takes the title of the hardest-working member of the royal family, undertaking the most royal engagements in a year.