Though the term "diptychs" is often applied loosely (and improperly) to almost any list of names for liturgical commemoration, it is used here in its proper technical sense for the diaconal proclamations found either in the anaphora or preanaphora of eastern eucharistic liturgies.Liturgy is about praying, and not just about praying to but also praying for. The diptychs are one of the ways Churches have prayed for the major historical personages with whom their destinies were interwined. But praying for implies whose side one is on. So the diptychs were an important factor in the politico-ecclesial relations between Byzantium and the West. In spite of their historico-politcal importance, no one has hitherto attempted a detailed historico-liturgical analysis of this important unit of Late Antique Byzantine Liturgy. That is what this short monograph attempts.