"Peter...at last, having come to Rome, he was crucified head-downwards; for he had requested that he might suffer this way." Origen, Third Commentary on Genesis, (A.D. 232).
"Thus Peter, the first of the Apostles, having been often apprehended, and thrown into prison, and treated with igominy, was last of all crucified at Rome." Peter of Alexandria, The Canonical Epistle, Canon 9 (A.D. 306).
"[W]hich Peter and Paul preached at Rome..." Lactantius, The Divine Institutes, 4:21 (A.D. 310).
"Peter...coming to the city of Rome, by the mighty cooperation of that power which was lying in wait there..." Eusebius, Ecclesiastical History, II:14,5 (A.D. 325).
"This man [Simon Magus], after he had been cast out by the Apostles, came to Rome...Peter and Paul, a noble pair, chief rulers of the Church, arrived and set the error right...For Peter was there, who carrieth the keys of heaven..." Cyril of Jerusalem, Catechetical Lectures ,6:14-15 (c. A.D. 350).
"And Peter, who had hid himself for fear of the Jews, and the Apostle Paul who was let down in a basket, and fled, when they were told, 'Ye must bear witness at Rome,' deferred not the journey; yea, rather, they departed rejoicing..." Athanasius, Defence of his Flight, 18 (c. A.D. 357).
I am going back to re-examine Clement of Rome, Justin Martyr, Ignatius, and will bring in Josephus [Jewish Historian] and Tacitus [Roman Historian] to see what they will tell us about this matter before us.
Irenaeus is the first one to say anything about Peter being in Rome [albeit with Paul and founding the church together with him]. None of these other writers told us that he had been there. Are they holding something back? Did they tell us everything? We will reexamine their writings to see what we can squeeze out of them and do all we can to make them cough it up.