The King's cancer treatment will continue into the New Year, it has been reported.
Palace sources told Sky News "his treatment has been moving in a positive direction and as a managed condition the treatment cycle will continue into next year".
They added there is “a sense of optimism”, with Charles keen to keep up a busy schedule of public engagements, including across Christmas.
It was announced in February that the King had been diagnosed with cancer and was beginning a course of treatment.
Charles took the decision to share his diagnosis in the hope it may help others, but has deliberately not confirmed the type of cancer he is being treated for so he doesn't detract from the significance of other forms of the illness.
It is also unclear what type of treatment he has specifically had, but he has regularly been in London for private appointments.
Dame Laura Lee, chief executive of the cancer support charity Maggie's, of which Queen Camilla is patron told Sky News: "It's very common for treatment to be ongoing for very long periods of time, as is the treatment that the Princess of Wales went through, which is an intense period of treatment over a year, and then it comes to a point where it's on an end, and she's on that recovery from some of the impacts of her treatment.
"So we've got immunotherapy, chemotherapy, surgery, hormone therapy. There are all sorts of different treatment modalities. And so it's not surprising at all."
Speaking about the impact the King and the Princess of Wales being open about his cancer diagnosis has had, she added: “What we've heard from our centre visitors, it's been good that they haven't just shone a light on one specific cancer type, but they've shone a light on cancer as a whole, and that there's varying treatment and varying impacts and varying different ways of navigating the challenges that cancer bring.
"And I think that approach has been much more effective and positive for the cancer community. I know firsthand that everyone is so grateful to them for doing that."
Charles has recently increased his number of engagements.
He hosted members of the Royal Family at Buckingham Palace for a pre-Christmas lunch yesterday. Today the King and Queen will hold their last public engagement of the year meeting local community volunteers, young people, emergency services, and faith representatives in Waltham Forest.
