The book includes the translation, annotation and study of 28 letters from the Registrum Epistularu of Saint Gregory the Great (540-604) related to the evangelization of the Angles. Gregorio’s letters configure the most direct and important documentation to interpret the nature of the missionary venture, which marked the history of Western civilization, insofar as it was configured as a paradigm of meeting of cultures in the context of the conformation of medieval Europe and the role of the Church as a promoter of this encounter and this conformation, in addition to representing a model of evangelization that has had echoes throughout history.