Papal visit: Pope Benedict and HM The Queen Pope Benedict leaves the Palace of Holyroodhouse in Edinburgh to begin the next stage of his four-day visit to the United Kingdom. (16 September 2010). Photo: ©Osservatore Romano

Papal Visit: Pope Benedict addresses civil society at Westminster Hall Pope Benedict meets former British Prime Ministers at the end of his address to civil society in Westminster Hall in the Palace of Westminster, London. (18 September 2010). Photo: ©Osservatore Romano

Papal visit: Welcome by HM The Queen Pope Benedict starts his visit by attending a State welcome ceremony at the Palace of Holyroodhouse in Edinburgh, and exchanges gifts with Her Majesty Queen Elizabeth II (16 September 2010). Photo: ©Osservatore Romano

Papal visit 2010: Pope Benedict lands at Edinburgh Airport Pope Benedict XVI is welcomed at Edinburgh Airport by His Royal Highness The Duke of Edinburgh on the first day of his visit to the United Kingdom (16 September 2010). Photo:©Osservatore Romano

HH Pope Benedict XVI greets TRH The Prince of Wales and The Duchess of Cornwall to a private audience in the Vatican, Monday 27 April 2009. © Photographic Service, Osservatore Romano

His Holiness Pope Benedict XVI receives British Prime Minister Tony Blair in Private Audience, 23 June 2007. (Copyright L'OSSERVATORE ROMANO - Photo Desk photo@ossrom.va)

In his capacity as President of the World Wildlife Fund (WWF), His Royal Highness The Duke of Edinburgh was received in Audience by His Holiness Pope John Paul II on 10 April 1990. Photo: ©Fotografia Felici

Her Majesty The Queen Elizabeth II and His Royal Highness The Duke of Edinburgh were received in private Audience by His Holiness Pope John Paul II on 17 October 1980. Photo: ©Fotografia Felici

Her Majesty The Queen Elizabeth II and His Royal Highness The Duke of Edinburgh were received in private Audience by His Holiness Pope John Paul II on 17 October 1980. Photo: ©Fotografia Felici

British Prime Minister Edward Heath's Audience with His Holiness Pope Paul VI, 4 October 1972. ©Fotografia Felici

The Archbishop of Canterbury Dr. Michael Ramsey paid a "solemn visit" to Pope Paul VI on 23 March 1966. He was received in the Sistine Chapel. On 24 March 1966, a Common Declaration was signed by Pope Paul VI and Dr. Ramsey in a ceremony held at the Basilica of St. Paul outside the Walls.©Fotografia Felici

The British Prime Minister Harold Wilson meets His Holiness Pope Paul VI in a private Audience (28 April 1965).©Fotografia Felici

The Prime Minister Mr. Harold MacMillan and The Lord Privy Seal Mr. Edward Heath were received in private Audience by His Holiness Pope John XXIII on 2 February 1963. They were also received by the Cardinal Secretary of State, His Eminence Amleto Giovanni Cardinal Cicognani. ©Fotografia Felici

Her Majesty The Queen and His Royal Highness the Duke of Edinburgh were reveived in Audience by Pope John XXIII during their State visit to the Vatican City on 5 May 1961.©Fotografia Felici