Queen Camilla expresses concern about King Charles' workload amid his cancer battle as she celebrates her 77th birthday, according to an expert.

Queen Camilla is currently concentrating solely on the king as she celebrates her 77th birthday.

King Charles III, wearing his Robe of State and Imperial State Crown, presided over the State Opening at Parliament, with Camilla by his side, wearing the George IV State Diadem.

According to Christopher Andersen, author of "The King," Camilla has been committed to assisting her husband, who is undergoing cancer treatment. Nevertheless, Andersen stated that the queen is concerned about the monarch's resumption of public duties as he continues treatment.

Andersen stated that Camilla has been a strong support for the king during his cancer battle.

"However, she is worried that Charles' headstrong ways may be hindering his recovery. She believes that he is not following doctors' orders as closely as he should. Any relief from the workload she has taken on is welcome, although despite Camilla's cheerful demeanor, you can see the strain on her face."

Andersen remarked that the king appeared healthy, but it was uncertain how well he was doing medically.

In April, Charles, 75, resumed public duties by visiting a cancer treatment charity. He and Camilla met with patients and staff at the University College Hospital Macmillan Cancer Centre in London during their visit.

Since February, the king has not participated in any formal public engagements, as he was taking a break to focus on his cancer treatment.

Since then, the monarch has been occupied with royal duties, with Camilla frequently accompanying him.

Royal photographer Helena Chard stated to Planet Chronicle Digital that Queen Camilla is a reliable source of support to her husband, King Charles, and is fully committed to her role of public service.

""She is working tirelessly on her 77th birthday, supporting the monarchy and shining brightly in white as she joins King Charles at the State Opening of Parliament. I'm sure she never imagined working on her birthday and is eager to spend a much-needed quiet and relaxing birthday with her family, away from the spotlight," said Chard."

The palace previously stated that doctors were "very encouraged" by the king's progress, but his schedule would be adjusted as necessary to safeguard his recovery.

Royal experts told Planet Chronicle Digital that there has been ample opportunity to celebrate Camilla's special day, despite her ongoing adjustment to Charles' comeback.

According to royal expert Hilary Fordwich, Prince William and Princess Catherine traditionally post tributes and share photos of Camilla on her birthday, along with birthday messages.

"Fordwich stated that in past years, the family has gathered at Clarence House for a small family dinner, and Charles hosts an evening get-together for guests back at Highgrove. She appreciates the public visiting The Queen’s Reading Room, where she celebrates everything related to books and the joy of reading."

Kate Middleton and Prince William celebrated Camilla's birthday by sharing a portrait of the queen on their Instagram Stories. The photo was taken by Kate for Camilla's "Country Life" cover in 2022.

Kate, 42, is also battling an undisclosed form of cancer.

"Regardless of who wears the crown, the birthday of an English queen is always a significant event, Andersen stated. In the morning, bells rang at Westminster Abbey, and the band outside Buckingham Palace played "Happy Birthday" during the Changing of the Guard. There were multiple cannon and gun salutes throughout the realm - in London, York, Edinburgh, and Cardiff. Despite having to attend work, Camilla sat by her husband's side, wearing full royal regalia, as Charles presided over the opening of Parliament and delivered the "King's Speech" outlining the new Labour Government's plans for the year."

Charles and Camilla were able to shed their ermine robes and gem-encrusted crowns - the king's Imperial State Crown is valued at upwards of $700 million - and relax, but not for long. Andersen continued. They usually celebrate birthdays by hosting a relatively intimate dinner party for family and close friends at Clarence House. Ironically, Camilla, who is such a skilled social planner, invariably winds up making all the arrangements for her own birthday parties.

"Camilla enjoys organizing the menu and seating arrangements for guests, comparing the task to moving pieces on a chess board. The king often selects eye-catching gifts from his late mother's jewelry collection for Camilla's birthday, including necklaces, earrings, bracelets, and pins. Some of these gifts have a history, having once belonged to earlier queens like Queen Victoria, Queen Mary, and the Queen Mother. The royals are discreet about showcasing their wealth, so these extravagant presents typically go unnoticed."

WATCH: HOW QUEEN CAMILLA WENT FROM VILIFIED MISTRESS TO BELOVED DAUGHTER-IN-LAW

Andersen remarked that these gifts are often overlooked until Camilla wears them in public at an event.

In a few weeks, Camilla and her husband will head to Balmoral in the Scottish Highlands, where they will spend the rest of the summer unwinding with family.

Andersen stated that they would spend the rest of summer engaging in activities such as fishing, hunting, riding, and hiking, in addition to hosting a variety of picnics, cocktail parties, dinners, and a formal ball.

In May 2023, Camilla was crowned queen after Charles became king upon the death of Queen Elizabeth II, who had been England's longest-reigning monarch and passed away in 2022 at the age of 96.

The Associated Press contributed to this report.