Battle of Ellandun
825 CE.
Shown on the map at 51.525°, -1.792°.
The Battle of Ellendun or Battle of Wroughton was fought between Ecgberht of Wessex and Beornwulf of Mercia in September 825. Sir Frank Stenton described it as "one of the most decisive battles of English history". It began the establishment of West Saxon dominance in southern England.
Text from the Wikipedia article Battle of Ellendun, licensed CC BY-SA 4.0.