Several times the monastery was in peril by reason of the wars between Wessex and Mercia. In A. D. 752, Cuthred of Wessex defeated Ethelbald of Mercia at Burford, hard by, and protected Abingdon from further aggressions. Twenty-five years later the decision of war was reversed. Offa, the great and fierce king of Mercia, defeated Cynewulf of Wessex, at Bensington, and spoiled the land, destroying the convent of St. Helena, founded by Cilla, and grievously robbing and oppressing Abingdon.