Vallum (Hadrian's Wall) - Archaeology and Purpose

Archaeology and Purpose

Before the middle of the 19th century, the Vallum was most commonly known as Agricola's Ditch, since antiquarians thought that it had been constructed during the period when Agricola was governor of Brittania, the Roman province spanning what is now England, Wales and southern Scotland. After John Hodgson published the final portion of his History of Northumberland in 1840, it became generally accepted that the Wall and Vallum had been built during the reign of Hadrian. Hodgson based his view on evidence which included a stone tablet in the Museum of Antiquities, Newcastle upon Tyne, which had been found in Milecastle 38 on the Wall in the previous century, its significance having been overlooked. The inscription on the tablet, probably made and erected to mark the completion of the milecastle, includes the names of Hadrian and Aulus Platorius Nepos (governor of Brittania during Hadrian's reign), as well as "Legio II Augusta" (Second Augustan Legion). It is now accepted that units of that Roman legion built the section of Hadrian's Wall which includes the milecastle, and they would have automatically included the names of the current emperor and governor on the tablet.

The first excavation was undertaken in 1893 at Great Hill (Heddon-on-the-Wall, near Newcastle upon Tyne), where it was observed that the Vallum ditch was cut through a seam of fire-clay which was deployed in both mounds. This excavation demonstrated that the main north and south mounds were contemporary and built using material dug from the ditch. In the late 20th century several excavations established that the marginal mound was also contemporary.

The Vallum is known to have been constructed some time after the wall was completed, as it deviates to the south around several wall-forts which were either completed or under construction when the wall was nearing completion. There would have been a crossing-point like a causeway or bridge to the south of each wall-fort—several such causeways are known, such as the one at Condercum in Benwell, a suburb of Newcastle. Causeways have also been detected to the south of several milecastles.

Although there is no definitive historical evidence as to why the Roman army built this unusual barrier, modern archaeological opinion is that the Vallum established the southern boundary of a military zone bounded on the north by the wall itself. The zone would have been "out-of-bounds" to civilians and those with no valid reason to be there.

Sometime in the 2nd century AD, the Vallum was "slighted"—that is, the ramparts were broken through and the ditch filled in at fairly regular intervals along its length. Archaeologists and historians have deduced that either the vallum was then deemed unnecessary, or that it was proving to be a hindrance to military and authorised civilian traffic. Some have suggested that this coincided with the building of the Antonine Wall in Scotland and the partial abandonment of Hadrian's Wall.