The King contacted both the Duke of Sussex and the Prince of Wales personally to tell them of his cancer diagnosis.

All of the King’s siblings, the Princess Royal, the Duke of York and Duke of Edinburgh, were also notified personally by Charles, 75, royal aides confirmed.

The Prime Minister was also informed of his condition.

Prince William, who returns to public duties this week after helping to settle his wife, the Princess of Wales, at home as she recovers from abdominal surgery.

He may also undertake some duties on behalf of his father, in addition to his own diary of  engagements, while the King undergoes treatment.

Palace aides said His Majesty was looking forward to returning to full public duty as soon  as possible. 

Counsellors of State, those appointed to stand in for the monarch if he is incapacitated, are not expected to be called upon.

A Buckingham Palace spokesman confirmed that the Queen “will continue with a full programme of public duties.”

Similarly, all working members of the Royal family will continue with a full programme of public engagements and may undertake some additional  duties on behalf of the monarch as required.