He arrived – in his own words, in 2005 – as “a simple, humble worker in God’s vineyard”. And on a grey, cold, blustery Monday in February, Pope Benedict XVI signed off in the same fashion: like an elderly labourer who can no longer ignore the pains in his back; who can no more count on the strength of his arms. Characteristically for this most traditionally minded of pontiffs, he made his excuses in Latin. The first German pope in modern times timed his departure to the minute. “From 28 February 2013, at 20.00 hours”, he told a gathering of cardinals in the Vatican, “the see of Rome, the see of Saint Peter, will be vacant and a conclave to elect the new supreme pontiff will have to be convoked by those whose competence it is.” 
Among those present was a Mexican prelate, Monsignor Oscar Sanchéz Barba, from Guadalajara. He was in Rome to be told the date for a canonization in which he has played a leading role. “We were all in the Sala del Concistoro in the third loggia of the Apostolic Palace,” he said. “After giving the date for the canonization, the twelfth of May, the Pope took a sheet of paper and read from it. 
“We were all left …” – Sanchéz Barba looked around him in the Bernini colonnade that embraces St Peter’s Square, grasping for the word, as speechless as the “princes of the church” who had just heard the man they believe to be God’s representative on earth give up on the job. “The cardinals were just looking at one another,” Sanchéz Barba said. 
Angelo Sodano, the Dean of the College of Cardinals, who must have been forewarned, delivered a brief and perhaps hurriedly composed speech. Before going on to assure the Pope of the cardinals’ loyalty and devotion, he said he and the others present had “listened to you with a sense of bewilderment, almost completely incredulous ”. At the end of his address, the Pope blessed those present, and left. “It was so simple; the simplest thing imaginable,” said Sanchéz Barba. “Then we all left in silence. There was absolute silence … and sadness.” 
John Thavis, who spent 30 years reporting on the Holy See and whose book, The Vatican Diaries, is soon to be published, said he had had an intuition the Pope might be about to resign and timed his return to Rome from the US accordingly. A fellow-Vatican watcher confirmed this to be the case. Thavis noted that in the book-length interview Benedict gave to a German journalist, published as Light of the World in 2010, he had made it clear he considered it would be right to go if he felt he were no longer up to the job. “I asked myself: if I were Pope and wanted to resign, when would I choose? He has completed his series of books and most of his projects are off the ground. What is more, there were no dates in his calendar of events he personally had to attend. I thought the most likely date was 22 February, which is the Feast of the Chair of St Peter. So I got it wrong.” 
The line emerging from the Vatican within hours of the announcement was that the Pope’s decision was a brave one. By this account, Benedict – never one to shrink from utterances and decisions that shocked – had taken it upon himself to bring his church face to face with reality: the reality that contemporary medicine can keep men alive far beyond the age at which they are up to grappling with the demands of running a vast global organization. Thavis agreed: “What I find particularly courageous is that he is prepared to say now, when he is not sick, that he is going; and that he’s doing it because he’s tired and not because he’s particularly ill.” But is that the whole story? Does he know more about his state of health than the Vatican has so far made public? 
Benedict’s own account of his reasons makes it clear that he took into account not only his physical, but also his psychological condition: “In order to govern the bark of Saint Peter and proclaim the Gospel, both strength of mind and body are necessary, strength which in the last few months has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfil the ministry entrusted to me.” Other theories will no doubt swirl around the Vatican in the days and weeks ahead, just as they did following the death of Pope John Paul I in 1978, 33 days after his election. Already there is speculation that something was about to come out about Benedict’s past. The Vatican will just as predictably dismiss such notions with contempt. But they are understandable all the same, for the transcendental importance of what Benedict has done cannot be overstated. 
Emerging from St Peter’s Basilica, Julia Rochester, from London, who described herself as a lapsed Catholic, was still turning over the implications of the Pope’s resignation. “If you’re God’s chosen one, how do you choose not be chosen?” she mused. It is a question many practising Catholics will be asking of their priests in the weeks ahead. In his first speech as Pope – humbly disclaiming his fitness for the task – Benedict said: “I am consoled by the fact that the Lord knows how to work and how to act, even with insufficient tools.” At some point in the last eight years, it would seem, he ceased to believe that was true.