According the the Anglo-Saxon Chronicle:

"In this year Ealdorman Ceorl with the contingent of the men of Devon fought against the heathen army at Wicganbeorg, and the English made a great slaughter there and had the victory. And for the first time, heathen men stayed through the winter on Thanet. And the same year 350 ships came into the mouth of the Thames and stormed Canterbury and London and put to flight Brihtwulf, king of the Mercians, with his army, and went south across the Thames into Surrey. And King, Æthelwulf and his son Æthelbald fought against them at Aclea with the army of the West Saxons, and there inflicted the greatest slaughter [on a heathen army] that we have ever heard of until this present day, and had the victory there."

"And the same year, King Athelstan and Ealdorman Ealhhere fought in ships and slew a great army at Sandwich in Kent, and captured nine ships and put the others to flight."