King Charles returns to royal duty and gives an update on cancer treatment

King Charles is preparing to return to public royal duties after revealing his cancer diagnosis in February.

Buckingham Palace shared an encouraging update on the royal's health on April 26, announcing that King Charles, 75, will visit a cancer treatment center to meet medical professionals and patients with Queen Camilla, 76, on April 30. It is understood that the center was not directly involved in the King's medical care.

The palace added that the outing would be the first of several engagements planned for the king in the coming weeks, including hosting a state visit at Buckingham Palace for the Emperor and Empress of Japan in late June.

After beginning cancer treatment, King Charles postponed his public duties but continued to work behind the scenes and hold meetings that included small audiences at Buckingham Palace. However, a royal source previously told PEOPLE that the King's desire to work “has not completely waned” with his nephew Peter Phillips revealing in an interview that his uncle was “frustrated” by the restrictions placed on him.

“He's always pushing his staff and everyone and his doctors and nurses to be able to say, 'Actually, can I do this?' 'Can I do that?' “Peter said. “So the overriding message is that he's clearly very keen to get back to some form of normalcy. And he's probably frustrated that his recovery is taking a little longer than he probably wants.”

A Buckingham Palace spokesman said King Charles' cancer treatment would continue, but “doctors are pleased enough with the progress so far that the King is now able to resume a number of his public duties.”

The king will continue all official state business and select audiences as well as adding public trips to his schedule, but will not have a full summer schedule, according to the palace. His appearance at Trooping the Colour, the annual celebration and parade marking the British monarch's birthday in London, on June 15, remains unconfirmed, as well as other notable events in the royal calendar such as Royal Ascot in June and the palace garden parties in May.

A palace spokesman said: “Any public engagements will be announced as soon as possible in the usual manner and will remain subject to the advice of doctors.”

The spokesman added: “His Majesty is very encouraged to resume some public duties, and is also very grateful to his medical team for their continued care and expertise.”

The latest health announcement was accompanied by a new photo of King Charles and Queen Camilla, taken to mark the approaching first anniversary of the coronation on May 6. The photo was taken in the gardens of Buckingham Palace on the morning of April 10, the day after the couple's 19th wedding anniversary, by portrait photographer Millie Pilkington.

Pilkington also posed behind the camera last year for official Christmas photos of Kate Middleton and Prince William's three children, Prince George, Princess Charlotte and Prince Louis. She also snapped a photo of the Prince of Wales surrounded by his sons and daughter which was released last year to celebrate Father's Day.

King Charles was recently spotted spending time with Queen Camilla in Scotland. On April 21, Queen Elizabeth's 98th birthday, the couple were photographed in a car after attending church at Crathie Kirk near Balmoral Castle, where the royal family traditionally gathers in the summer months.

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The king made his first major public appearance since revealing he had cancer on Easter. After attending a Mass at St George's Chapel at Windsor Castle with Queen Camilla and other members of the royal family, he greeted well-wishers outside by shaking their hands and wishing them a happy holiday.

A royal source told PEOPLE last month that King Charles was “progressing well” with his cancer treatment and that there was “a lot of confidence” amid the cutting-edge treatment he is receiving.

“He is positive and the doctors are optimistic,” the source said.