Seventy-five-year-old Charles had suspended public duties in February after being diagnosed with cancer while he was being treated for an enlarged prostate the previous month.

In a setback for Prince Harry, the younger son of King Charles III, a High Court judge in London ruled against his legal challenge concerning the level of his security protection in the UK. The court determined that the decision to reduce police protection for the prince while he is in his home country was not "unlawful or irrational."

"During The King's recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted. Subsequent diagnostic tests have identified a form of cancer," reads the Buckingham Palace statement.