King Charles is carrying out his first major public engagement since his cancer diagnosis.

The King, who has been named Cancer Research UK's new patron, and Queen Camilla are visiting a specialist cancer centre in London in support of staff, patients and ongoing research.

Aside from an Easter Sunday church service, the King has stayed away from public events and crowds.

But a statement issued last week had a more positive message about his 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 means he is able to begin a gradual return to public engagements, starting with the symbolic trip to the Macmillan Cancer Centre at University College Hospital in central London 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 is intended to continue the King's desire to raise awareness of the importance of early cancer diagnosis, It follows the monarch's decision to make public his own health issues earlier this year, in the hope it will encourage others to seek health checks.

A smiling photo of the King and Queen was issued together with positive messages about his health

There will also be the opportunity to see some of the innovative technology and cancer research, supported by Cancer Research UK, taking place at the hospital.

During his visit, he will meet the charity's chief clinician, Professor Charlie Swanton, who has led a project tackling various cancers.

Although the mood music about the King's health is more positive, it remains a cautious optimism, with the King's cancer treatment still continuing and no date announced for its completion so far.

However, he is expected to be sufficiently well to host a state visit from the Emperor and Empress of Japan in late June, which forms part of his role as head of state.

Despite his recent convalescence, the King has carried on with his constitutional role, including regular private meetings with the prime minister.

Nonetheless, it remains uncertain whether the King will 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 will be able to take part will be made following medical advice nearer the time, but the King's summer schedule is likely to be reduced, or adapted, while he continues his recovery.