Prince William, Kate Middleton Send King Charles Birthday Greeting On Social Media

The British royal family is celebrating King Charles III's 74th birthday.

Prince William and his wife Kate Middleton kicked off the tributes for the King by sending their birthday wishes via Twitter Monday.

"Wishing a very happy birthday to His Majesty The King!" the Prince and Princess of Wales captioned a picture of the King smiling.

The snap was taken during King Charles' visit to Yorkshire, England, last week, according to People. He toured Morrisons Supermarkets headquarters to learn more about the grocery hub's sustainability initiatives and apprenticeship programs during the royal outing.

Buckingham Palace also greeted the monarch, tweeting, "Wishing His Majesty The King a very happy birthday today."

Monday marked King Charles' first birthday since he acceded to the throne following the death of Queen Elizabeth II in early September.

King Charles reportedly celebrated the occasion in private and did not make a public appearance, according to the Daily Mail.

But public celebrations were held across London. The Household Cavalry Band performed a rendition of the "Happy Birthday" song during the Changing the Guard ceremony outside Buckingham Palace.

A video of the tribute was shared via the royal family's official Twitter account.

Gun salutes were also fired across the city, with the King's Troop Royal Horse Artillery, which does salutes on major events such as state visits, firing 41 volleys at London's Green Park at midday.

This was followed by the Band of the Scots Guards also performing the "Happy Birthday" song in the park and the Honorable Artillery Company firing a 62-gun salute at the Tower of London.

King Charles has been traveling all over the U.K., fulfilling royal duties, leading the nation in mourning the longest-serving British monarch's death, as well as preparing for his coronation to be held on May 6, 2023, at Westminster Abbey in London.

Over the weekend, the King led the nation in paying tribute to the fallen members of the British Armed Forces on Remembrance Sunday at the Cenotaph in Whitehall. In his floral tribute, the monarch wrote the words, "In memory of the glorious dead. Charles R," according to the Daily Mail.

King Charles also faced criticism from anti-monarchy protesters in the two months since he acceded to the throne.

Last week, while King Charles and his wife, Queen Consort Camilla, 75, were on an official visit to York, England, for the unveiling of a statue of Queen Elizabeth, the couple was nearly hit with eggs by a protester.

Four eggs were thrown by a protester, later identified as activist Patrick Thelwell, as he shouted, "This country was built on the blood of slaves." He was escorted away by police officers and the royal staff following the incident.

Despite one of the eggs landing near the King's feet, he seemed unbothered by the incident, stepping over the mess to continue greeting royal fans alongside his wife.

Meanwhile, King Charles' younger son Prince Harry and daughter-in-law Meghan Markle have yet to greet the monarch on his birthday.

The Duke and Duchess of Sussex's relationship with the royal family reportedly remains strained following the couple's decision to leave royal duties in 2020 and relocate to California, where they now live with their two children, 3-year-old Archie and 1-year-old Lilibet.