Prince William is worried for his 'workaholic' father King Charles during his cancer recovery, those close to the Royal Family have revealed. The King, 75, has told friends about his determination to beat the illness and return to work.

But his son is said to fret about a hectic schedule for a man of advanced years fighting a serious illness and wants him to balance recovery and Royal duties.

A source close to William said: “He wants to make sure his father is balancing his recovery. He knows his dad loves work, but he does worry about him.”

Those close to the monarch recognise it is a hectic schedule for any septuagenarian, let alone one undergoing cancer treatment. The King was seen this week at the Royal Windsor Horse Show sharing a hug with niece Zara Tindall, which an expert claimed showed the depth of their "effortless connection".

King Charles III attends the Endurance event on day 3 of the Royal Windsor Horse Show at Windsor Castle on May 03, 2024 (
Image:
Getty Images)

The King returned this week to public duties following treatment for the disease, his diagnosis of which was announced back in February. King Charles appeared emotional at one engagement following his cancer diagnosis - and gave an update on how he was feeling.

He looked relaxed and in good spirits during a visit to the University College Hospital Macmillan Cancer Centre in London where he learned about some of the latest treatments and sat down to chat to patients receiving chemotherapy and also met staff.

The King sympathised with one cancer patient as she received her chemotherapy with many others in a day unit, telling Lesley Woodbridge, 63: "I've got to have my treatment this afternoon as well." When quizzed about his health, he told one patient: "I’m alright thank you very much, not too bad."

King Charles III, patron of Cancer Research UK and Macmillan Cancer Support, and Queen Camilla, arriving for a visit to University College Hospital Macmillan Cancer Centre, London (
Image:
PA)

It has also been revealed that he has written letters to friends outlining his determination to beat his illness. He is described as being like a "caged lion" and frustrated by his cancer diagnosis because he's got so much more to achieve, an insider told The Times.

The King and Queen are to take on more than 200 new patronages amidst a major reshuffle of 1,000 roles. He is understood to be keen to focus on those with a focus on community, commonwealth, climate and culture.

Doctors are said to be “sufficiently pleased with his progress” to allow a summer programme of duties for the King. Next month he will host a state visit by the Emperor and Empress of Japan.

Prince William, Prince of Wales stands to attention during a visit to The Lord High Admiral's Divisions at Britannia Royal Naval College on December 14, 2023 (
Image:
Chris Jackson/Getty Images)

The Palace has said that the King’s diary in the coming months will involve “a few engagements a week” while he continues with treatment.

But there are a number of important engagements on the horizon this summer which he will be determined to attend. He will hope to travel to Normandy on June 6 to commemorate the 80th anniversary of the D-Day landings, with the Prince of Wales also expected to join him.

At a palace reception last week, the Queen, 76, spoke of her husband's eagerness to return to duties. Camilla said the King was "really thrilled to be out" this week but admitted: “I've been trying to hold him back”.