Princess Anne politely refused Queen Camilla's attempt to break royal protocol.

During a joint engagement at the University of London's Foundation Day, Princess Anne stopped Queen Camilla from breaking royal protocol.

On Wednesday, the University of London's chancellor, Anne, 74, presented Camilla, 77, with an honorary doctorate of literature to recognize the queen's promotion of literacy and literature for over two decades.

Before entering the room at the Senate House, Camilla invited the Princess Royal to go in first.

The Daily Express reports that Anne, who is knowledgeable about royal etiquette, "graciously declined and let Camilla go in first."

At formal and state events, the royals follow a "sequential hierarchy of nominal importance," as stated by the outlet.

Despite being the only daughter of the late Queen Elizabeth II and Prince Philip, Camilla, as queen, holds a higher position in the order of precedence than Anne.

According to royal tradition, Camilla should enter the room before Anne.

Camilla and Anne were among the five recipients of honorary doctorates and their families, as reported by the Daily Express. While in the room, Camilla was captured on camera smiling as she signed a visitor's book.

According to the outlet, Anne inspected a Guard of Honour made up of members of the university's Officer Training Corps, Air Squadron, and Royal Naval Unit before the ceremony.

Camilla and Anne put on formal attire for the doctorate presentation. During the event, Camilla was seen sitting on a stool while Anne placed a hood on her sister-in-law's head.

Camilla smiled as she held her diploma while posing for photos with the two later.

The University of London was founded in 1836 by Royal Charter and began conferring honorary degrees in 1908 during its Foundation Day ceremony.

Buckingham Palace announced that King George V, Queen Mary, the Prince and Princess of Wales, and Camilla received honorary degrees.

Other notable recipients include Sir Winston Churchill, Dame Judi Dench, and T.S. Eliot.

The palace announced that Her Majesty, as an avid reader, has a strong interest in literacy and has long been a supporter of literacy in the UK and across the Commonwealth. She has visited schools, libraries, workplaces, and prisons to see the work of adult literacy schemes.

The Duchess of Cornwall, as Her Majesty, serves as the patron of several organizations that promote and support literacy, including the National Literacy Trust, First Story, Coram Beanstalk, and BookTrust.

"In January 2021, the Queen’s Reading Room launched as an online book club on Instagram, featuring reading recommendations from Her Majesty Queen Camilla, then Duchess of Cornwall. It later evolved into a charity promoting the benefits of reading in February 2023."

The wedding of King Charles III and Camilla in 2005 was a special moment for the two friends, who have been close for many years.

In 1970, Charles and Camilla started dating, but they ended their relationship in 1971 when the future king enlisted in the Royal Navy.

While Camilla married Andrew Parker Bowles in 1973 and Charles married Princess Diana in 1981, the two later resumed their romance while still married to their respective spouses.

In 1995, Parker Bowles and Camilla divorced, while Charles and Diana finalized their split in 1996, a year before the Princess of Wales' tragic car accident in 1997.

In the 2023 BBC documentary "Charles III: The Coronation," Anne praised her sister-in-law.

"Anne, who has known the queen for a long time, praised her understanding of her role and its impact on the king in a Daily Express interview.

"Although this role may not have been a natural fit for her, she excels at it and brings a change of pace and tone to the performance."