Interesting idea from the Hexham Courant:
A CONTROVERSIAL archaeologist has turned received wisdom on its head to explain the purpose of the 112km vallum running the length of Hadrian’s Wall.
The trench – 6m wide and up to 3m deep – is unique in Roman construction and has long been the source of debate.
Located a few metres to the south of Hadrian’s finest achievement, the majority verdict is that it was a barrier providing additional protection for the Wall itself.
Another suggestion is that it helped contain livestock, delineating grazing land at the foot of the wall for the herds kept by the Roman forts.
However, Tynedale-based structural archaeologist Geoff Carter, the man who previously floated the theory the Roman Wall was first constructed in timber, believes differently.
It is, in fact, the construction trench for a road that was abandoned when the scale of the project became unwieldy, he claims.
“The vallum is unique, always a problem to archaeology, where insights so often come from comparing things,” he said.
“However, there is a simple and less ambiguous explanation for the creation of the vallum; it is a construction trench for a road that was never completed.
“The quality of a road, or other civil engineering project, was a reflection of the person who initiated and sponsored it.
“A Roman politician’s prestige and standing was, in part, a reflection of the nature and quality of the engineering ‘good works’ that bore his name.
“In this context, a plan to construct a high quality properly bedded, road along Hadrian’s new frontier is not surprising.”
When it was constructed, the vallum ran in an unbroken line the length of the Wall, so it would have provided a link between each of the forts along the way.
It had often been observed that its construction mirrored that of a Roman road, in that it had long straight stretches linked by gentle bends, and it avoided soft ground and steep gradients.
In the central section, where the Wall ran along the crags of the Whin Sill, the vallum stayed down in the valley.
And the only places where it was interrupted was where the causeways would have been that led into the forts and some of the milecastles.
“Most authors have sought to explain the vallum as a physical boundary that defines some form of military zone, restricting access to or from the Wall,” said Geoff.
“Like the Wall itself, the vallum would have represented a formidable obstacle to north-south movement.
“But the ambiguity of this explanation arises from the observation that a simple bank and ditch could have served this function more efficiently, and might be considered standard practice in the circumstances.”
He was sure the trench had been dug to house a road bed for a central carriageway, and the two parallel lines of spoil heaps – still in evidence today – set back on either side to allow room for the lanes used by riders and pedestrians.
However, the project to build a road linking the forts between the bridgehead at Newcastle and the west coast still had a long way to go.
A huge workforce would have had to be brought in for the more highly skilled construction phase, and around three million tons of aggregate and a mortared stone capping were required to do the job.
Geoff said: “If we accept the vallum was a military road, abandoned during construction, then it adds further weight to the arguments that the building of Hadrian’s Wall was interrupted, and then scaled down when work was resumed.
“The form, layout and route of the vallum all indicate that this earthwork was a road, albeit an unfinished one. This is the only rational engineering explanation.”
The vallum — a.k.a. Agricola’s Ditch — and its purpose are actually the subject of a separate Wikipedia entry which does hint at the controversy about its purpose. This theory is somewhat attractive, but the 3m deep aspect of it seems rather ‘deep’ for road construction, no? See, e.g., the useful info at the Birmingham Roman Roads Project … the ‘shape’ seems okay, but the depths are a bit extreme … Then again, a map at the same site speculates that a road ran along the wall (and the ‘other’ wall too). I wonder if there’s a handy list of archaeological finds from along/within the vallum …
UPDATE (the next day): It turns out the archaeologist (Geoff Carter) has a blog of his own (very interesting, by the way) and has blogged about this idea in much more detail: Reverse Engineering the Vallum