The King has led royal tributes to Pope Leo XIV after he was diagnosed with lung cancer.
Charles, 77, who was himself diagnosed with the disease in 2024, has written privately to the Pontiff to pass on his well-wishes, HELLO! understands.
The exact contents of the King's message are not known.
The King and Queen Camilla held a private meeting with Pope Leo at the Apostolic Palace last October during their rescheduled state visit to Vatican City.
© GettyHe became the first British monarch to pray with a pope publicly since 1534, when King Henry VIII split with the church.
Charles and Camilla previously visited the Vatican in April 2025, meeting Pope Francis.
Charles himself continues to undergo cancer treatment, though he revealed that this had been "reduced" at the start of the year.
Prince Albert and Princess Charlene's tribute
Also expressing well wishes on Wednesday were Prince Albert and Princess Charlene, who said they were "deeply moved" in a statement shared on social media. The Monégasque royal couple met with the Pontiff just two weeks ago.
The personal letter, dated 12 October and signed with the Prince's official signature, was sent on behalf of Princess Charlene and their family, including 11-year-old twins Prince Jacques and Princess Gabriella.
© POOL/AFP via Getty ImagesPrince Albert wrote that the family had felt "comforted" by the Pontiff's decision to undergo surgery, saying: "Princess Charlène and I, along with our Family and the entire Principality, wish to assure You of all our filial support and our fervent prayers."
The letter, which has been translated into English from French, continued: "In assuring Your Holiness of our closeness during this time of trial, we pray that once the operation is completed, your healing and full recovery will follow quickly, allowing you to continue with all your strength your ministry, which the world needs now more than ever."
"Deign, most Holy Father, Your Holiness, to accept our most faithful and respectful devotion," he concluded.
Latest as Pope Leo is diagnosed with lung cancer
Pope Leo underwent surgery on Tuesday, after which he was diagnosed with lung cancer, the Vatican said.
The 71-year-old had a successful operation to remove a lower lobe in his right lung after announcing news of his operation during his weekly Sunday prayers in Rome.
Tests confirmed a diagnosis of lung adenocarcinoma after a 90-minute surgery at Rome's Gemelli hospital, where well-wishers gathered outside.
The Vatican said in a statement: "The operation was successful and there were no complications.
"After the operation, the Pope awoke normally and returned after a brief period of operation to his room".
© Getty ImagesHe is expected to remain in hospital for around a week, while his audiences have been cancelled until 20 October.
Pope Leo was elected head of the Catholic Church on 8 May 2025 following the death of Pope Francis that April at the age of 88.
Prince Albert and Princess Charlene's close relationship with the Pope
Monaco has a close relationship with the Vatican, as the Roman Catholic faith is recognised in the constitution and they have a longstanding diplomatic relationship.
Prince Albert and Princess Charlene met Pope Leo in September for a conference called "At the Roots of Europe: For Peace and Unity".
© Getty ImagesThe royal couple was also joined by President Emmanuel Macron of France and his wife Brigitte, who were wearing black, and Grand Duke Guillaume of Luxembourg.
Charlene exercised her "privilege du blanc" – the privilege of wearing white – which permits the heads of state of Catholic countries to wear white in the presence of the Pope.
She also exercised the rare privilege back in March, when Pope Leo visited the Principality of Monaco, while Albert and Charlene were received at the Vatican in January.
© GettyThe historic March visit marked the first apostolic journey by a Pope to Monaco in the modern era. Pope Paul III had previously been received on the Rock in 1538.
Monaco’s palace described that papal visit as a powerful sign of "hope" centered on "dialogue, peace and shared responsibility".
During his Monaco visit, Pope Leo also emphasised the Principality’s potential role in bringing people together.
