The Pope will travel to Portugal this week amid hopes that he might shed light on one of the Catholic Church's most intriguing mysteries – the so-called Third Secret of Fatima

By Nick Squires in Rome
Published: 10:50PM BST 09 May 2010

During his four day visit, Benedict XVI will pray at the shrine of Fatima, one of the best known centres of Catholic pilgrimage in the world and the focus of endless conspiracy theories and Doomsday predictions.

Its cult is founded on the belief that three shepherd children witnessed a series of apparitions and prophecies of the Virgin Mary in 1917.

The third secret was only disclosed by the Vatican in 2000 and was said to have foretold the assassination attempt on Pope John Paul II by a Turkish gunman in 1981.

There has been intense speculation ever since that the Vatican withheld part of the secret, which is said to have concerned the Satanic infiltration of the Catholic Church, the rise of an anti-Pope or even nuclear Armageddon. The Holy See claims that it has released the full text of the secret and that it is holding nothing back, but many Catholics are not convinced.

Benedict is one of the world's leading authorities on the mystery because as Cardinal Joseph Ratzinger, before he was elected Pope in 2005, he was responsible for developing the Vatican's official position on the miracle of Fatima and wrote a scholarly interpretation of the Third Secret.

Benedict's visit is heavy with symbolism. He will be in Fatima on May 13 – the same day, in 1917, that the Madonna supposedly first appeared to the children. It is also the date on which Turkish gunman Mehmet Ali Agca came close to killing John Paul II after shooting him in St Peter's Square.