GIOVANNI DIACONO, called HYMONIDES. - B. ca. 825, d. before 882. A monk of Monte Cassino and friend of Anastasio Bibliotecario, he exercised great influence at the Curia of Pope Giovanni VIII (872–82). Charged by him with writing the biography of St. Gregorio Magno, he composed the most extensive life of the great Roman Pope, which remains the best among the ancient biographies, written with sound historical judgment, in thematic rather than chronological form, according to the four books of the Regula pastoralis.
His literary authorship of other works is not fully established. According to Latin sources, at the request of Gaudericu di Velletri he began a life of St. Clemente Romano, and rendered into 575 verses the apocryphal Convivium (Symposion), commonly called Caena Cypriani (v.), of St. Cipriano. His collaboration on the Liber Pontificalis is probable.