 She first witnessed a charter dated 770, along with Ecgfrith and Ælfflæd.By 780 she is "Cyneðryð Dei gratia regina Merciorum" ("Cynethryth, by the Grace of God, Queen of the Mercians").It has been suggested that Cynethryth's coinage was in emulation of the Byzantine Empress Irene, who ruled during this time through her son Constantine VI.