King Charles III was not happy when Prince William and Kate Middleton were late to his coronation last year, according to royal biographer Robert Hardman’s book, “The Making of a King: King Charles III and the Modern Monarchy.”

In the book, per People magazine, Hardman claimed that Charles, 75, and Queen Camilla, 76, were early to the coronation at Westminster Abbey in London, England, on May 6, 2023.

The Prince and Princess of Wales were supposed to be there eight minutes before the king and queen consort, but they arrived “a minute and a half late” with their two younger children, Princess Charlotte, 9, and Prince Louis, 6.

Hardman described the situation as “an awkward scene,” and explained that the delay in the coronation created “an added layer of stress” for Charles and Camilla.

King Charles III and Queen Camilla on the balcony of Buckingham Palace on the day of his coronation.AP

The author also revealed a lip reader’s translation of what Charles said in footage captured on a Sky News camera as he was waiting for his son and daughter-in-law.

“We can never be on time … There’s always something … This is boring,’” Hardman claimed the monarch said.

Prince William (from left) and Kate Middleton with their son Louis and daughter, Charlotte, arriving at King Charles III’s coronation.AP

Prince William (center) with his family at his dad King Charles III’s coronation ceremony on May 6, 2023.POOL/AFP via Getty Images

Hardman learned from sources that William, 41, and Middleton, 42, were possibly late because they created a coronation video the morning of the affair.

Staff for the couple, meanwhile, told Hardman that their car got caught behind Charles and Camilla’s cavalcade, which wouldn’t have happened if the king didn’t arrive early.

“It is unusual for the two most important arrivals at such a significant event, and over such a well-trodden route, to be so unpunctual,” Hardman wrote in his book. “The result is some frantic rewriting of the running order. There isn’t time for the Waleses and their two younger children to enter ahead of the King and Queen. They must now follow behind and bring up the rear.”

Despite the brief snafu, the coronation went off without a hitch and Charles was named Britain’s new monarch.

“I come not to be served but to serve,” Charles declared at the ceremony.

King Charles III travels to Westminster Abbey before his coronation ceremony on May 6, 2023.AP

He formally came into power after the death of his mother, Queen Elizabeth, at the age of 96 in September 2022. She ruled for more than 70 years.

Charles has remained largely out of the limelight since announcing his cancer diagnosis in February. He underwent a procedure for an enlarged prostate, and doctors discovered “a separate issue of concern” that requires treatment.

Buckingham Palace later clarified that the cancer was not prostate cancer.

King Charles III after being crowned during his coronation ceremony.Getty Images

The king, who is currently receiving outpatient treatment, resumed his royal duties last week by attending several engagements, including the Royal Windsor Horse Show in Berkshire, England.

Middleton is also battling cancer at the moment.

The mother of three shared her diagnosis with the world on March 22.

She’s been on hiatus from her public royal duties since January.