LONDON (Reuters) -Britain's King Charles on Saturday expressed gratitude to well-wishers following his cancer diagnosis, his first public comment since Buckingham Palace announced he would postpone some engagements to undergo treatment. "I would like to express my most heartfelt thanks for the many messages of support and good wishes I have received in recent days," Charles said in a statement. The palace announced on Monday that Charles, 75, had been diagnosed with a form of cancer, less than 18 months into his reign.