KING Charles has officially returned to public royal duties, eleven weeks after announcing he has cancer.
But a royal expert has claimed that Prince William will be worried about his father's return and is "fiercely protective" over him.
On Tuesday, Charles, 75, swapped stories and held hands with patients as he visited a cancer treatment centre with the Queen, 76.
When asked about his health battle and recovery, His Majesty understandably said it was a "bit of a shock" to be given his cancer diagnosis.
Former BBC Royal Correspondent Jennie Bond said that William, who has reduced his own engagements to care for Kate as she recovers from surgery, will be looking out for King Charles.
She told : “William and Charles have become so much closer in recent years, particularly after Harry's exit, so I'm sure William feels fiercely protective towards his father.
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"But he knows about his work ethic so I think William will just have to accept that he has little choice but to trust that Charles won't push himself impossibly hard during these first months of treatment."
She added that the King is known to be a "workaholic", with early-morning starts and post-midnight finishes.
Jennie said that William and Harry once revealed that Charles often gets preoccupied with paperwork and falls asleep at his desk.
The former BBC Royal Correspondent claimed that King Charles is keen to prove himself in as a capable and present monarch.
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It has been speculated whether King Charles could make an appearance at both Royal Ascot and Trooping the Colour - both taking place in June.
However, Jennie added that Camilla is also “hugely protective” about her husband doing too much too soon.
The palace has only so far confirmed the King's cancer hospital engagement, which took place yesterday, and an upcoming Japan State Visit.
They did also confirm The Sun's story last month that planning is underway for the King to travel abroad which includes D-Day 80th anniversary commemorations in June and even Australia in October.
The palace spokesperson added: "Planning continues for ways in which Their Majesties may attend such summer and autumn engagements, though nothing can be confirmed or guaranteed at this stage.
"All future plans remain subject to doctors' advice nearer the time, with appropriate adaptations made where necessary to minimise any risks to His Majesty’s continued recovery."
It is understood the King's programme will be "carefully calibrated" with his medical team as his recovery continues.
Timeline of King Charles' health battle
January 17: Buckingham Palace announces the King has been diagnosed with enlarged prostate
January 26: The Sun exclusively photograph the King arriving at The London Clinic for his 'corrective procedure'
January 29: Seen waving and smiling as he left hospital after an extra night
February 5: Palace reveal while in hospital for his prostate operation doctors discovered the the King has a form of cancer
February 10: King issues 'heartfelt thanks' in a written statement
February 21: King tells Rishi Sunak he had been "reduced to tears" by get well cards
March 21: Princess of Wales and King have lunch at Windsor Castle
March 22: Kate announces via video statement that she is being treated for cancer
March 31: King attends Easter Sunday service and tales part in 'walkabout' with members of the public and aides say 'it was a significant step' as KIng had 'responded to treatment very encouragingly'
April 4: The Sun exclusively reveals King has ordered aides to 'supercharge' his diary for the summer and is 'raring to go'
April 10: King and Queen embark on break at Birkhall, in Scottish Highlands
April 26: Buckingham Palace announce King will return to public-facing front-line duties
Future:
April 30: King will mark his public comeback by visiting a cancer hospital with the Queen
May 8 and 21: Buckingham Palace Garden Parties
May 21 - 25: Chelsea Flower Show
June 6: 80th anniversary D-Day commemorations in France and UK
June 15: Trooping the Colour birthday parade in London
June 17: Garter Day parade at Windsor Castle
June 18 - 22: Royal Ascot
Late June: State Visit by Emperor and Empress of Japan
July 3: Holyrood Week in Scotland
October: Two or three week tour of Australia
The spokesperson said: "His Majesty is greatly encouraged to be resuming some public-facing duties and very grateful to his medical team for their continued care and expertise."
His comeback comes just days before the nation will celebrate the first full year since the King's Coronation last May.
His Majesty and Princess Kate have been confiding in each other amid their shared cancer shocks.
Charles is very eager to have his time as King to carry out his role as fully as possible
Jennie Bond
The royal mum-of-three, 42, opened up about her diagnosis in an emotional video last month.
Like her father-in-law, doctors detected the disease after she went in for planned abdominal surgery in January.
As Princess Kate and King Charles have taken a step back, Prince William and Queen Camilla have stepped up to shoulder the burden of their royal duties.
Everything we know about King Charles' return to work
Q: Does today's announcement mean King Charles' cancer treatment has been successful or finished?
A: The King's treatment programme is ongoing but doctors are "sufficiently pleased" with the progress so far and Charles is now able to resume a number of public-facing duties. Further royal engagements will be adapted where necessary to cut down on any recovery risks.
Q: How much longer will King Charles receive treatment?
A: While it is too early to say, the King's medical team are "very encouraged" by progress made so far and remain "positive" about his recovery.
Q: How many engagements will King Charles undertake in the weeks and months ahead.
A: They will be announced nearer the time in the usual manner and will remain under doctor's advice. It will not be a full summer programme. His Majesty will continue with all official State business and selected Audiences.
Q: Is there a risk King Charles may be taking on too much with these external duties?
A: The King's schedule will be carefully designed to meet his recovery needs and he will be in close consultation with his medical team.
Q: Will King Charles attend the Birthday Parade, D-Day Commemorations, Garden Parties, Royal Ascot, or an Autumn overseas Tour?
A: Planning continues for ways in which the King and Queen can attend these summer and autumn engagements. All future plans remain under doctor's advice.
Q: How is King Charles feeling?
A: The Palace said: "His Majesty is greatly encouraged to be resuming public-facing duties and very grateful to his medical team for their continued car and expertise."
Recently, Wills visited a school in Sandwell, West Midlands to meet a boy, 12, who wrote him a heartfelt letter about the stigma around male mental health.
The royal apologised for Kate's absence and said she would have "loved to be there."
Meanwhile, Queen Camilla continues to be the King's "rock" - and is said to be in regular contact with Kate.
The Queen has continued to carry out all of her royal duties and attended many events by herself after urging Charles to slow down.
She attended 13 royal engagements in the month after His Majesty's health announcement.
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In March, she jetted off for a well-deserved break as one of the last key royals standing amid Kate and Charles' rest.
But, Camilla dutifully returned on March 11 to stand in for the king at the Commonwealth Day service at Westminster Abbey.
Charles’ docs are ‘positive’ about King’s cancer recovery
KING Charles’ doctors are “positive” about his cancer recovery as he heads back to work 11 weeks after his diagnosis.
The monarch is well enough to return to front-line public-facing duties, Buckingham Palace has announced.
Palace officials say the King, 75, is still undergoing cancer treatment but his medical team are “very encouraged by the progress” and “remain positive” about his recovery.
Charles will be joined by Camilla, 76, as he chooses to make his public comeback by visiting a cancer hospital to speak to staff and patients, together on Tuesday.
The palace has also confirmed he will host a State Visit from the Emperor and Empress of Japan this summer.