King Charles III celebrates his first birthday on the throne Monday.

The monarch is 74 years old.

Buckingham Palace shared a new photo of King Charles in honor of his birthday that shows him leaning against a tree in Windsor Great Park.

"The King has officially become Park Ranger of Windsor Great Park, 70 years after his father, The Duke of Edinburgh, was appointed to the post," the palace tweeted. "The Ranger offers guidance to the Deputy Ranger and his team in the day-to-day stewardship of one of the country’s oldest estates."

Prince William and Duchess Kate Middleton also shared a photo of Charles on their own Twitter account.

"Wishing a very happy birthday to His Majesty The King!" they wrote.

The royal family releases a photo of King Charles on his birthday

The royal family shared multiple photos of King Charles III on Twitter to mark the monarch's 74th birthday. (Twitter: Royal Family)

Charles celebrates his birthday as "The Crown" thrusts his affair with now Queen Consort Camilla back into the spotlight. The fifth season of the Netflix drama explores the hardships the royal family faced in the 1990s, including Charles' divorce from Princess Diana.

KING CHARLES III AND CAMILLA HURLED WITH EGGS, PROTESTOR ARRESTED

It took years for many in Britain to forgive King Charles, whose admitted infidelity and longtime links to Camilla torpedoed his marriage to Diana, known as "the People’s Princess."

Royal author Angela Levin spoke to Fox News Digital about the king's relationship with Camilla.

Levin said that for years, Camilla struggled with the public breakdown of Charles and Diana’s marriage. At the time, she was depicted as a "wicked woman" who maliciously tore the couple apart. She was vilified as "a marriage wrecker" once more during the fourth season of "The Crown," which detailed the royal love triangle. Viewers were so enraged that Charles and Camilla’s Clarence House Twitter account had to turn off comments due to the backlash.

King Charles and Camilla wave

King Charles III and Camilla, Queen Consort, wave as they leave Dunfermline Abbey after a visit to mark its 950th anniversary on Oct. 3, in Scotland. (Andrew Milligan - Pool/Getty Images)

Charles and Camilla first dated after being introduced at a polo match in 1970. She was 23, and Charles was considered the most eligible bachelor in Britain. The two instantly became close, but the romance was interrupted by Charles’ eight months of naval duty.

The couple split in 1973 when Charles went off to sea. Camilla went on to marry Andrew Parker Bowles that same year. Charles married Lady Diana Spencer in 1981. According to reports, Charles and Camilla rekindled their romance in 1986. Then in 1993, an intimate phone call between Charles and Camilla leaked, rocking the palace and confirming the persistent reports of an affair.

Prince Charles and Princess Diana wedding

King Charles III's birthday is celebrated as the fifth season of "The Crown" thrusts his affair with now Queen Consort Camilla back into the spotlight. Charles kept a relationship with Camilla going while married to Princess Diana. (Terry Fincher/Princess Diana Archive/Getty Images)

NETFLIX'S ‘THE CROWN’ SEASON 5 PUTS CAMILLA'S SCANDALOUS ROMANCE WITH KING CHARLES BACK IN SPOTLIGHT

Princess Diana wearing a hat

Princess Diana’s full name was Diana Frances Spencer. She died on Aug. 31, 1997, following a vehicle collision in Paris. (Getty Images)

Tragedy struck in 1997 when Diana died from injuries she sustained in a Paris car crash at age 36. Two years later, Camilla and Charles made their first public appearance. The couple said "I do" in a private ceremony in 2005.

The public mood has softened since Camilla became a member of the royal family. She has taken on roles at more than 100 charities, focusing on a wide range of issues, including promoting literacy, supporting victims of domestic violence and helping the elderly. Charles appears more relaxed beside her as they take on royal duties together.

Ahead of the release of the new season of "The Crown," Netflix added a disclaimer to highlight that the series is fictional.

The YouTube and Twitter handles of the series now say, "Inspired by real events, this fictional dramatization tells the story of Queen Elizabeth II and the political and personal events that shaped her reign."

The streaming giant also claimed the show "has always been presented as a drama based on historical events," BBC News reported.

Prince Charles and Princess Diana

Charles claimed in his own 1994 biography that he was forced into the marriage with Princess Diana (seen in 1991) by his late father, Prince Philip. The two finalized their divorce in 1996. (Jayne Fincher/Princess Diana Archive/Getty Images))

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The disclaimer noting the series is fictional followed backlash from many, including Dame Judi Dench.

"While many will recognize ‘The Crown’ for the brilliant but fictionalized account of events that it is, I fear that a significant number of viewers, particularly overseas, may take its version of history as being wholly true," she argued in a letter to the Times of London. 

"Given some of the wounding suggestions apparently contained in the new series – that King Charles plotted for his mother to abdicate, for example, or once suggested his mother’s parenting was so deficient that she might have deserved a jail sentence – this is both cruelly unjust to the individuals and damaging to the institution they represent."

King Charles laughing with wife Camilla

King Charles III and Camilla wed in 2005. (Rob Jefferies/Getty Images)

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Fox News Digital's William Mendelson and Stephanie Nolasco contributed to this report.