Battle of Hingston Down

The Battle of Hingston Down took place in 838 at Hingston Down in Cornwall between a combined force of Cornish and Vikings on the one side, and West Saxons led by Egbert, King of Wessex on the other. It resulted in a West Saxon victory.
The British kingdom of Dumnonia, which covered Devon and Cornwall, survived into the early eighth century, when eastern Devon was conquered by Wessex. Conflict continued throughout the 8th century with Wessex pushing further west. In 815 King Egbert raided Cornwall 'from east to West' which, given later battles at Gafulford and Hingston Down probably indicates the conquest of the remaining parts of West Devon.
In 838 the Cornish allied with "a great ship army" of Vikings to fight the West Saxons, but were defeated at Hingston Down. This was the last recorded battle between the Cornish and the West Saxons and ended roughly a century of warfare that began at the Battle of Llongborth in 710 (see Geraint of Dumnonia). The last known king of Cornwall, Dungarth, died in 875, but he is thought to have been an under-king subject to Wessex. King Athelstan set the modern day boundary of the county at the Tamar, indicating continued cultural and ethnic distinction, albeit under his overlordship.