The Codex epistolaris Carolinus preserves ninety-nine letters, dated between 739  and 791 and sent by the popes to the Frankish king Charlemagne and his predecessors. The compilation was commissioned by Charlemagne in 791, but the sole surviving medieval manuscript of the letters was made at Cologne in the later ninth century and is now in Vienna (Österreichische Nationalbibliothek Cod. 449). The headings or lemmata provided for each letter by the Frankish compilers in 791 and faithfully preserved in the codex, add a distinctive Frankish commentary on events in Rome and Italy in the second...