By Sean Coughlan, BBC News
King Charles is to carry out his first major public engagement since his cancer diagnosis.
The King and Queen Camilla will visit a hospital and specialist cancer centre, in a public show of support for staff, patients and ongoing research work.
Aside from attending an Easter Sunday church service, the King has stayed away from public events and crowds.
But last week Buckingham Palace issued a statement with a more positive message about the monarch's health.
The King's doctors were said to be "very encouraged by the progress made so far" in his treatment for an unspecified form of cancer.
It meant he was able to begin a gradual return to public engagements, starting with the symbolic trip to a cancer centre on Tuesday.
The King's recent personal experience of cancer, which was diagnosed in February, will bring an additional significance to his visit to the hospital - where he will pay tribute to the staff's efforts on behalf of patients, families and carers.
The visit was intended to continue the King's desire to raise awareness of the importance of early cancer diagnosis. It followed the monarch's decision to make public his own health issues earlier this year, in the hope it would encourage others to seek health checks.
There would also be the opportunity to see some of the innovative technology and cancer research taking place at the hospital.
Although the mood music about the King's health was more positive, it remained a cautious optimism, with the King's cancer treatment still continuing and no date announced for its completion so far.
However, he was expected to be sufficiently well to host to a state visit from the Emperor and Empress of Japan in late June, which formed part of his role as head of state.
Despite his recent convalescence, the King had carried on with his constitutional role, including regular private meetings with the prime minister.
Nonetheless, it remained uncertain whether the King would be able to attend some of the key royal events taking place in the weeks ahead, including Trooping the Colour, garden parties and D-Day commemorations.
Decisions on whether he would be able to take part would be made following medical advice nearer the time, but the King's summer schedule was likely to be reduced, or adapted, while he continued his recovery.
- BBC