Offa (ŏfˈə) [key], d. 796, king of Mercia (757–96). He succeeded
Æthelbald to the throne, but it was some years before he
attained the power of his predecessor. Gradually he asserted his
overlordship in Kent and then Sussex, and by 774 his charters
styled him rex Anglorum [king of the English]. He restricted
Cynewulf, king of Wessex, to the area S of the Thames and in 794
had Ethelbert, king of the East Angles, beheaded and thereafter
ruled his kingdom. In time the rulers of Wessex and Northumbria
became his sons-in-law. In 786 the pope sent two legates to him,
and by 788 Offa had set up an independent archbishopric of
Litchfield, thus wresting control of the churches in Mercia from
the hostile archbishop of Canterbury. He introduced a new
coinage in the form of the silver penny, which for centuries was
to be the basis of the English currency. Offa had sufficient
standing in Europe to negotiate with Charlemagne as an equal;
and, although they quarreled over a proposed marriage of their
children, they signed (