King Charles, 75, faces a cancer diagnosis after a hospital procedure for benign prostate enlargement.
Buckingham Palace disclosed the diagnosis and announced the postponement of the King's public engagements.
The King has begun regular treatments and will continue state business and paperwork during this period.
He expressed gratitude to his medical team and remains positive about his treatment, aiming to return to public duties soon.
King Charles informed his sons, Prince William and Prince Harry, about the diagnosis himself.
Prince William is in regular contact with his father, while Prince Harry is expected to travel to the U.K. soon.
Prince William is resuming public duties after supporting his wife, Kate Middleton, during her recovery from abdominal surgery.