Clement relates the anecdote in the sixth book of: `The Outlines` [Hypotyposes], and Papias, bishop of Hierapolis, also bears witness to it and to Peter mentioning Mark in his earlier letter. Indeed they say that he composed it at Rome itself, and that he indicates this when referring figuratively to the city as Babylon in these words: `The elect [the church] that is in Babylon greets you and so does my son Mark` ((EH 2. 15, 1-2 and RO 166)).
`And again in the same books, Clement states a tradition of the **very earliest presbyters** about the order of the gospels; and it had this form. **He used to say that the first written** of the gospels **were those having the genealogies**. And that the Gospel of Mark had this formation. **While Peter was publicly preaching** the Word in Rome and proclaiming the gospel by the spirit, **the audience**, which was numerous, **begged Mark**, as one who had followed him for a long time and remembered what had been said, **to write down the things he had said**.
And he did so, handing over the Gospel to those who had asked for it. And when Peter got to know about it, he exerted no pressure either to forbid it or to promote it … But John, last of all, being conscious that the exterior facts had been set forth in the [other] Gospels, after he had been urged by his friends and divinely moved by the Spirit, composed a spiritual Gospel`. ((EH 6:14, 5-7 and RO 166r)).
In this last paragraph above, Clement of Alexandria clearly sets down which two gospels were the first to be written - Matthew and Luke. He is the only early historian to specifically write concerning the chronology of the Gospels. He said he was quoting the very earliest presbyters [note in the plural]. Other writers did not dispute his evidence.