Pope Francis offered an affectionate, public thank you to Benedict XVI, whose retirement from the papacy in 2103 shocked the Roman Catholic Church and the world.

Addressing tourists and Romans in St Peter’s Square, Francis triggered applause when he recalled that it was the 70th anniversary of Benedict’s ordination to the priesthood in his native Germany.

Joseph Ratzinger later became a powerful Vatican official as the church’s official guardian of doctrinal orthodoxy.

Then, in 2005, Ratzinger was elected by fellow cardinals as pontiff and chose the name Benedict XVI.

He announced in February 2013 his decision to retire two weeks later, the first pontiff to resign in 600 years.

Benedict, now 94 and frail, is devoting his remaining years to prayer in a monastery in Vatican City.

Francis said: “To you, Benedict, dear father and brother, goes our affection, our gratitude and our closeness.”

Francis then noted in his remarks that Benedict “lives in the monastery, a place desired to host the contemplative community here in the Vatican, so that they may pray for the church”.

“Currently, he’s the Vatican’s contemplative one, who is spending is life praying for the church and for the diocese of Rome, of which he is emeritus bishop,” Francis said.

“Thank you, Benedict, dear father and brother.

“Thank you for your credible witness,” Francis added.

He concluded with yet another expression of gratitude, saying: “Thanks for your gaze continuing turned toward the horizon of God, thank you.”

Some Church observers have expressed discomfort at the reality of having a retired and current pontiff both living at the Vatican.

Others criticised the retirement decision itself.

Francis, 84, pays occasional calls on Benedict at the monastery.

The current pope has also indicated that if, like Benedict, he feels he no longer has the strength to adequately carry out a pontiff’s mission to the church, he might consider resignation himself.