The King has been seen in public for the first time since his cancer diagnosis as he left Clarence House the day after starting his treatment, following a brief reunion with the Duke of Sussex.
Charles and the Queen were driven away from their London residence to Buckingham Palace, before being flown by helicopter to Sandringham in Norfolk.
The Duke of Sussex is said to have been reunited with the King after making a transatlantic dash to be with his father following the shock news.
Harry arrived in London from California on Tuesday afternoon, without the Duchess of Sussex and their children, less than 24 hours after the announcement about the King’s health was made to the nation by Buckingham Palace.
The short meeting between Charles and his youngest son has raised hopes the pair will be reconciled despite their troubled relationship.
But their first face-to-face encounter for many months appeared to last for as little as 45 minutes before the King left for his flight to Sandringham.
Suggestions the duke could also heal his long-running rift with his brother, the Prince of Wales, look unlikely.
It is understood the Prince of Wales has no plans to meet with Harry.
William is juggling looking after his wife, the Princess of Wales, with caring for their children after Kate’s abdominal surgery.
Dressed in a suit and tie and smart overcoat, the King waved and smiled at well-wishers, with Camilla at his side in the back of the car, as they left Clarence House just after 3.30pm.
A helicopter was seen flying from Buckingham Palace just 10 minutes later.
The King, 75, has postponed all public-facing duties, but is continuing with behind-the-scenes work on his red boxes of state papers.
He usually has a weekly audience with Prime Minister Rishi Sunak on Wednesday.
Mr Sunak has revealed more of Charles’s condition, saying he was thankful the King’s cancer has been “caught early” as he wished him a full recovery.
Asked what the diagnosis meant for the day-to-day running of the country, Mr Sunak told BBC Radio 5 Live: “We’ll crack on with everything.”
During the pandemic, the late Queen carried out her audiences with the PM on the phone, and with the King at Sandringham this looks the most likely option, unless they opt for a video call.
Buckingham Palace confirmed the King, who only acceded to the throne 17 months ago, does not have prostate cancer, saying only that it was a “form of cancer”.
He was diagnosed after a “separate issue of concern was noted” and investigated while he was being treated for his benign enlarged prostate.
Harry’s black Range Rover was pictured arriving at a private terminal at Los Angeles International Airport before he boarded a flight for London, and he was later seen at Clarence House.
He last appeared alongside the Windsors at the King’s coronation in May, but hurried home immediately afterward to mark his son Prince Archie’s fourth birthday.
The duke’s allegations against his family appeared unrelenting in the aftermath of Megxit with his Oprah interview, and, in the months following the Queen’s death, his Netflix documentary and memoir Spare.
There were accusations of racism in relation to Archie’s skin tone before he was born – with the remarks in the end alleged to have come from two senior royals – and claims Kensington Palace lied to protect William over reports he allegedly bullied Harry out of the royal family.
Harry claimed Charles was jealous of Meghan and Kate, did not hug him when he told him his mother Diana, Princess of Wales had died, and said he believed the King was “never made” for single parenthood, but “to be fair, he tried”.
The duke also accused William of physically attacking him and throwing him into a dog bowl in a row over Meghan, teasing him about his panic attacks, and, along with Kate, encouraging him to wear a Nazi uniform at a fancy dress party.
Charles, according to Harry, pleaded with his sons during a tense meeting after the Duke of Edinburgh’s funeral: “Please, boys. Don’t make my final years a misery.”
While Charles and Harry were said to still speak, William has reportedly not been in contact with his brother for an extended period of time.
William is returning to official duties this week, beginning with an investiture on Wednesday.
The heir to the throne is expected to also be undertaking some duties on his father’s behalf, but Counsellors of State, who are appointed temporarily when a monarch cannot fulfil their duties as head of state, are not expected to be needed.
Meanwhile, the Princess Royal held the fort on the royal engagements front, carrying out an investiture on behalf of the King at Windsor Castle on Tuesday.
Charles personally called both Harry and William, as well as his siblings Anne, the Duke of York and the Duke of Edinburgh, to give them the news before it was publicly announced to the nation by the Palace at 6pm on Monday.
The Palace has called for the King’s privacy to be respected, especially during his treatment, but said he wanted to make his diagnosis public because of his long-running support for cancer charities.
This is the latest major royal health scare to hit the monarchy at the start of 2024, coming after the King’s hospital stay, Kate’s major surgery, keeping her away from official duties until after Easter, and Sarah, Duchess of York’s skin cancer diagnosis.