The monarch is said to have turned to Archimandrite Ephraim for spiritual advice after the health scare, which has prompted him to postpone all public-facing duties.
The two men struck up a friendship in the late 1990s, when the King visited Elder Ephraim’s Vatopedi monastery on Mount Athos in Greece on multiple occasions.
Elder Ephraim, 67, said he had spoken to the monarch, adding that they enjoy a “very good rapport”.
“Yes, he has been in contact since the diagnosis and I believe he’ll overcome it. Charles has a spiritual sophistication, a spiritual life,” he told a Greek newspaper and television station.
Three of those visits took place between spring 2003 to May 2004, with the then Prince of Wales reportedly refusing the presence of Greek officials.
The King has long maintained a deep fascination with all religious faiths, from Islam to Buddhism, and has worked to bring different faith leaders together.
The King’s interest in the Orthodox Church has seen him speak out in defence of persecuted Christians in the Middle East.
Byzantine icons at Highgrove
The King has visited Vatopedi Monastery at Mount Athos, Greece, several times. Photo / Getty Images
In 2004, it was claimed that he had become so enamoured with the Orthodox faith that he had adorned a section of his Highgrove home with prized Byzantine icons, many said to originate from the Mount, the Orthodox world’s holiest site.
He was anointed with chrism oil hailing from the Mount of Olives in Jerusalem, where the King’s paternal grandmother, Princess Alice of Battenberg, is buried.
The King will miss a thanksgiving service for his close friend and second cousin, King Constantine of Greece, this week as he continues his treatment for cancer.
Instead, the Queen will lead members of the royal family as they gather in St George’s Chapel, Windsor Castle, in honour of the former ruler and last King of Greece, who was toppled from the throne in the 1960s in a military coup.
Constantine II was a first cousin once removed and sailing partner of Prince Philip. He died at the age of 82 in January last year. The King had a close friendship with Constantine, choosing him as a godfather for son William, now the Prince of Wales.
Constantine’s widow, Queen Anne-Marie, their eldest son Crown Prince Pavlos and other members of the Greek royal family will fly to the UK for the memorial service in the nave of the 15th-century chapel in Berkshire.
However, the King is not expected to see them, even privately, as he seeks to reduce public interactions.
King Charles III reads cards and messages, sent by well-wishers following his cancer diagnosis. Photo / Getty Images
Last week, the King said he had been moved to tears by well-wishers after receiving 7000 cards and letters from across the world following his cancer diagnosis. Sitting at a desk in a room in the 18th Century Room of Buckingham Palace’s Belgian Suite, he is seen laughing at a card featuring an illustration of a dog.
The pet was wearing an Elizabethan collar - better known as the “cone of shame” - after having veterinary treatment, with a caption reading: “At least you don’t have to wear a cone!”
The picture was released after footage showed the King meeting Prime Minister Rishi Sunak which marked the King’s first in-person audience since mid-December, and his first engagement since his cancer diagnosis was confirmed on February 5.
