Following the direct consultation of the illuminated manuscript of Iviron monastery which contains both an 11th-century Greek text of the Life of saints Barlaam and Ioasaph and an early-13th century fragmentary translation, transcribed on the (now amputated) margins of the former text, the Author unravels the stages of the translation process into vernacular French. Since a codicological analysis of the manuscript is impossible, given that its folios have been cut and inserted into modern support pegs, the analysis is based on the chronology of ink colours and that of the revision process. This leads to the conclusion that the vernacular text was translated and revised by a team of scribes, one of whom was a certainly a scholar of Greek, while the other was a speaker of Romance. Further proof is given that the translation was written on the bound manuscript, at a much later date that the writing of the Greek original, and that the ink of the vernacular text wore off when overlapping golden Greek majuscules.