A royal expert has provided an update on the health of the King after he returned to public duties yesterday.
His Majesty had his first official engagement since being diagnosed with cancer and he visited the University College Hospital Macmillan Cancer Centre with the Queen and met patients and staff in his new role as the charity's patron.
Speaking to GB News, royal commentator Jennie Bond said: "The King is being more than monitored. He's been treated.
"In fact, he was having a treatment just yesterday afternoon. He confided in one of the patients that he was having his treatment.
"We don't know what treatment that is, but he did discuss the cold cap, which is used during chemotherapy with another patient. Maybe that's what he's having. But certainly, the treatment is ongoing."
She also revealed that the monarch's outfit choice could be an indicator of his mental wellbeing.
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Bond said: "He was wearing his favourite tie, it is his C Rex tie. It's got little dinosaurs on it.
"And he wears that when he's feeling pretty cheerful."
She added: "I haven't actually been in his wardrobe, but he has lots of very beautiful silk ties. And he does take special pride in wearing particular ties.
"Obviously on ceremonial occasions, he wears the appropriate tie, but this is a rather amusing one. It's got little dinosaurs.
"So it's a play on C rex, and I think we can deduce from that he was feeling a little bit playful, certainly upbeat."
GB News host Isabel Webster pointed out that she thought the daring accessory could have been a gift from one of his grandchildren.
In the past Prince Louis has been reported as dinosaur-mad, so the accessory could be a present from him.
The tie could also be a nod to an inside joke shared with his beloved family, as Charles uses the initial R after his name to signify "Rex" - which is Latin for "King."
In photographs, The King looked overjoyed to be back performing duties for the first time since his cancer diagnosis, smiling and holding the hands of patients on the chemotherapy ward.
The King, who has become Cancer Research UK's new patron, was shown some of the innovative medical technology at the Macmillan Cancer Centre at University College London Hospital.
But there was a sense of shared human experience as he sat down to chat with patients about the treatment they were receiving - sympathising that he had his own "treatment this afternoon as well".