Last week /u/TheSpaceWeegee asked about Roman persecution of the early Christians and I wrote a lengthy answer going over the phases of the Roman state's involvement. There is, within that tale but with details omitted in my answer, a particular oral/church tradition that I find rather interesting and this seems like a good thread to expand some thoughts on it. This bit of Church History carries on now as oral tradition, but it actually was written down at first. There's little information to prove it did happen and even less to prove it did not. The only possible forensic evidence is in the possession of the Roman Catholic Church.

I'm referring to the story of the Crucifixion of Saint Peter and the trivia of where the story comes from.

#The Oral Tradition - Quo Vadis

The popular story goes that after escaping the jail in Jerusalem (Acts of the Apostles 12), Saint Peter the Apostle eventually went to Rome, founded the church there, and served as its Bishop and the first Pope.

During the reign of Nero, in the wake of the Great Fire, the Roman Emperor scapegoated the Christians for the fire and began a mass persecution. Saint Peter is said to have initially fled the city, but saw a vision of Christ heading into Rome while carrying a Cross. Saint Peter asked him, "Where are you going?" (Quo Vadis) Christ answered, "I am going to Rome to be crucified again." Saint Peter returned to Rome and is said to have been crucified by the Romans, specifically requesting to be crucified upside down because he was not worthy of the same fate as Christ.

#Origin

The origin of this story is the Apocryphal Acts of Peter which was written sometime in the later Second Century, somewhere in the neighborhood of 100 years after the death of Saint Peter. What survives of the Acts of Peter can mostly only be found in the Codex Vercellensis and was never considered Biblical canon. It is curious, then, that this story had become an oral tradition within the Christian Church. Perhaps its poetic potency for the faithful was significant enough that Quo Vadis was borrowed from the otherwise disregarded text and merged with other oral traditions.

#Complementary Tales & Written Records

Another such tradition is that on Saint Paul the Apostle. According to the Biblical account, Acts of the Apostles, Saint Paul had demanded trial by the Emperor himself and was being transported to Rome. Despite its order in Biblical Canon coming before the Pauline Epistles, Acts 28 ends with Saint Paul preaching in Rome from his home while waiting two years for the Emperor to have time for his trial.

Oral Church tradition says that Saint Paul was beheaded in the same persecutory frenzy that followed the Great Fire. There are no contemporary accounts of this, though it was also written down later. Like Saint Peter, any forensic evidence of Saint Paul's death is in possession of the Roman Catholic Church.

The earliest non-apocryphal account of Saints Peter and Paul being killed in Nero's persecution come from Pope Saint Clement of Rome. sometime between AD70 and AD140, a time ranging from almost immediately after Nero's reign to almost a century after the events, Pope Saint Clement wrote a letter to the Church in Corinth which contains references to the martyrdom of Saint Paul and in Rome, but is rather vague concerning the martyrdom of Saint Peter and makes no mention of where or how it occurred.

First Clement, as the letter is known, is the earliest such reference for quite some time. Saint Ignatius of Antioch in the early second century indicated such a tradition had already existed by that time, and from that time on many Church Fathers and Roman Historians wrote about the deaths of Saints Peter and Paul, though most probably had taken this Church Tradition for granted as factual.

There is no other record of Saint Peter ever having even been to Rome beyond this tradition. Romans did sometimes crucify victims in various positions and were not completely predisposed to ignoring any such potential request for a particular position, were it to grant any sort of novelty to the event.

There is a rival tradition, though very minor in number of Christians that believe it, that the escape from prison detailed in Acts 12 is actually describing Saint Peter's death in a Jerusalem jail.

#Forensic Records

As mentioned, all possible forensic records are in possession of the Catholic Church. The purported tomb of Saint Peter under Saint Peter's Basilica is said by the Catholic Church to contain remains of a man that died in his 60s. In 1968 and again in 2013, the Catholic Church have affirmed these remains as those of Saint Peter.

In 2002, a tomb was discovered near the Basilica of Saint Paul Outside-The-Walls. In 2005 the Catholic Church announced this was the tomb of Saint Paul and in 2009 affirmed that their archaeological excavations supported conclusion that it belonged to Saint Paul. Carbon dating reportedly indicated the body of a man who died in the 1st Century.

#References & Readings on Church History

Acts of the Apostles by Saint Luke.

Acts of Peter by Unknown Author.

First Clement by Pope Saint Clement of Rome.

Letter to the Ephesians by Saint Ignatius of Antioch.

Church History by Eusebius.

Prescription Against Heretics by Tertullian.

The Orthodox Faith, Volume III, Church History by Father Thomas Hopko.

Concerning Lowliness of Mind by Saint John Chrysostom.

Annals by Tacitus.

The Jewish War by Josephus.

Journal of Biblical Literature by Donald Fay Robinson.