From BBC:
King Charles and Pope Leo are to become the first British monarch and pontiff to pray together at a church service since the Reformation in the 16th Century.
This historic moment will be in the Sistine Chapel in the Vatican, during next week’s state visit by King Charles and Queen Camilla. Under the chapel’s famous ceiling painted by Michelangelo, the service will bring together clergy and choirs from both the Roman Catholic church and the Church of England, of which the King is supreme governor.