Princess Anne served a very special duty for her older brother, King Charles III, at his coronation on Saturday.

The Princess Royal, 72, changed out of her coronation robes and played security guard for the monarch, 74.

The mother of two was on horseback in the parade out of Westminster Abbey, following the crowning ceremony.

According to Royal Central, Anne is “Gold-Stick-in-Waiting, meaning she is The King’s personal bodyguard for this procession.”

She led 6,000 armed services personnel through London in what was called the coronation procession.

Anne rode behind the carriage carrying Charles and his wife, Queen Camilla, after the religious service.

She spoke about her official role on May 4, telling CBC News: “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.”

She continued: “So that is a role I was asked if I’d like to do for this coronation, so I said yes. Not least of all, it solves my dress problem.”

The Gold-Stick-in-Waiting role dates back to the 15th century, with the monarch protected by two rods made of gold and silver.

During the coronation, Anne donned her military uniform and a wild red feathered hat.

Charles’ son, Prince Harry, had his view hilariously blocked by her enormous cap during the liturgy.

The Duke of Sussex, 38, was spotted strategically trying to maneuver his head around the giant plume to see the ceremony better.

Anne, however, didn’t seem to notice, as she was seen chatting with a guest, seemingly unaware she was obstructing Harry’s view.

Elsewhere, Anne spoke about how her brother is adjusting to being king following the death of their mother, Queen Elizabeth II — Britain’s longest-reigning monarch.

“Well, you know what you’re getting because he’s been practicing for a bit, and I don’t think he’ll change,” she shared, before adding. “You know, he is committed to his own level of service, and that will remain true.”

The royal was also asked about the idea of a “slimmed-down” monarchy, noting that the concept was initially raised within The Firm “when there were a few more people around.”

“It doesn’t sound like a good idea from where I’m standing, I would say. I’m not quite sure what else we can do,” she said.