Alfred's Castle farmhouse was built within the abandoned prehistoric enclosure. King Alfred won a great victory against the Danes at the Battle of Ashdown, in AD 871. Being located just to the west of Ashdown House, Victorian antiquaries associated Alfred's Castle with the King's troop movements before the battle. The exact site of Alfred's battle has not yet been determined, however, so is a matter for debate. The most likely sites are near Compton and Aldworth in Berkshire. Excavations were carried out at Alfred's Castle from 1998-2000 by archaeologists from Oxford University, and post-excavation analysis is still ongoing (as of August 2011).
Halfdan Ragnarsson led by Bagsecg, bolstering the ranks of Halfdan's army. According to the "Anglo-Saxon Chronicle", the Danes battled the West Saxons nine times, including the Battle of Ashdown on 8 January 871. However, the West Saxons could not be defeated, and Halfdan accepted a truce from Alfred, newly crowned king of Wessex. The Army retreated to the captured town of London and stayed there over the winter of 871/872. Coins minted in London during this period bear the name Halfdan, identifying him as the leader of the army. In autumn of 872 the Army returned to Northumbria to quell a revolt