Hadrian’s Wall is impressive, even in decline. A massive stone boundary striding across today’s landscape, its very size sends out messages: ‘It was intended as a defensive line’; ‘It was built to impress’; ‘It marked the edge of Caesar’s land’. These are all matters that we continue to probe today. We also argue about the date that the army started to build it, and how long it took them. On this subject, we have little to go on. A statement in ancient literature penned over two centuries after the event attests that Hadrian came to Britain and was the first to build a wall 80 miles long to separate the Romans and ‘barbarians’. A handful of inscriptions and the evidence offered by archaeological investigations offer further clues. Yet we in Britain are lucky: this is quite a lot of evidence compared to other frontiers.
We can work out that it was in AD 122 that Hadrian visited Britain, and building inscriptions associated with the Wall bear his name. Nevertheless, we have nothing that tells us when the monumental task of building was completed. No ancient author states ‘this was the year that Hadrian’s Great Wall was finished’, or words to that effect. No inscription has been found recording that it was the last stone to be laid on the Wall. In order to seek an answer to the question, ‘Was Hadrian’s Wall finished by the death of the emperor in AD 138?’ we have to turn to archaeology.
In 1986, to his great surprise, Jim Crow found an extra tower on Hadrian’s Wall. The turrets along the Wall – in reality towers, but named after the Latin turres – were regularly spaced, but between turrets 39a and 39b, close to the centre of the Wall, there sat an extra tower. Its history proved to be equally interesting: it was not an original part of the blueprint for the Wall, but butted against it – the Wall itself had been built in two phases, with a significant gap between them. After the foundations had been laid, it seems, building work paused long enough for a layer of peat 600mm (2ft) deep to develop at the place where the tower was to be erected. Further indication of a lengthy hiatus was that a bonfire large enough for its ashes to spread on both sides of the Wall had been lit, which suggests that a considerable amount of scrub had grown over the abandoned foundations.
This was not the first time that evidence for a break in the building programme had been noted. Almost a century earlier, in 1894, Francis Haverfield – widely regarded as the founder of the study of Roman Britain – began a programme of excavations along Hadrian’s Wall that was to last ten years. He was not able to solve all the questions on his list, but he did open our eyes to other issues. One was at Chesters, where, in 1900, he dug a series of trenches intended to determine whether the ditch of Hadrian’s Wall passed under the fort. He located the ditch in a trench in the middle of the fort, and at the bottom discovered what he described as ‘a substantial layer of peat, with traces in it of moss and of wood (alder and birch – one piece retaining its silver bark, and looking as if cut by a knife), some animal’s bones (a small piece of deer’s antler, etc), a bronze nail, and some leather, which appeared to be a bag and a strap.’ This layer was 45cm (18 inches) thick: further evidence of a pause in the building programme. In short, the Wall ditch had been dug and, as Ian Richmond was to discover later, the adjacent turret at least partly built, before the work stopped. When it resumed, peat intermixed with Roman artefacts had accumulated in the ditch.
Another step forward came with the publication of Tony Wilmott’s excavation of Birdoswald fort in 1997. There, a layer of soil was recorded across the area inside the west gate, overlying the courses that had already been laid. Scrub had grown on this soil, only to be burned off when building recommenced. Pottery from the site indicated that the builders returned to complete their task still within Hadrian’s reign.
Hints of disruption
These three excavations provide evidence for a break of some duration in the building programme; clearly the task of constructing Hadrian’s Wall did not proceed smoothly. There are other hints of disruption too. At Great Chesters, the foundations of the Wall had been laid but not built on. When, after a break of indeterminate length, the soldiers returned, they ignored the existing works and built their section of the Wall on new foundations immediately to the south of the abandoned stones. The same phenomenon may be observed some four miles (6.5 km) to the east too.
Great Chesters also offers another clue to the length of time it took to build Hadrian’s Wall. A building inscription found at the east gate of the fort honours Hadrian as Pater patriae, ‘Father of his country’, a title he only accepted in AD 128. It is true that a few early inscriptions elsewhere wrongly give him this title, but would such a mistake be made along the Wall, in a military landscape littered with official inscriptions? It seems unlikely. The Great Chesters inscription dates to at least six years after Hadrian’s visit to Britain, and there are even later inscriptions from the 130s. A case in point is the fort at Carrawburgh, where a partially preserved inscription almost certainly refers to Julius Severus and therefore dates to about 130–132. The fort is an addition to the Wall but was built under Hadrian (this is based not only on the inscription but on Hadrianic pottery found during excavations there). Work was also undertaken at the fort at Carvoran in 136/137.
This evidence indicates that the construction of Hadrian’s Wall was a long, drawn-out process. But is there any evidence that the task was not finished during Hadrian’s reign? Indeed, such evidence has long been known. At Limestone Corner, beside milecastle 30, the fact that Roman excavators had failed in their task of digging out the ditch to its full depth can be seen today, with large stones still sitting in it. A little way to the east, the work of smoothing out the upcast mound had been abandoned, leaving ridges of earth stretching northwards from the ditch. Elsewhere, in a few locations, a small bank may be observed on the north lip of the ditch, probably a marking-out bank; if the spreading of the earth from the ditch had been completed properly the bank would have been covered by the soil from the ditch. Both of these examples relate to the ditch, however, and there has been, to date, no suggestion that they might point to the Wall itself being unfinished.
Evidence from inscriptions
There is nevertheless growing evidence that other elements of the frontier were still not completed by the end of Hadrian’s reign in AD 138. Here, again, Tony Wilmott’s excavations at Birdoswald are important. Tony not only found that there was a pause in the building programme, but that two elements of the fort were incomplete. The digging of the outer ditch had not been finished, nor were the granaries erected.
Moreover, Birdoswald – like all the forts that projected north of the Wall – was provided with additional side gates, as if expecting the construction of a road behind the Wall. Such a road, the Military Way, was indeed provided, but not until the return from the occupation of the Antonine Wall in the 150s or 160s.
The evidence that we have at our disposal shows that work on building Hadrian’s Wall proceeded in a staccato fashion, with breaks in progress observed at several sites, some indicating a gap of some duration. At the end of the reign of Hadrian, work on some elements had not been completed. Can we go further?
The building inscriptions from Hadrian’s reign are mostly simple in design: the name of a centurion – perhaps also his cohort, sometimes a legion – is cut on the face of a simple building stone, creating what is generally known as a ‘centurial’ stone. But at various locations along the Wall, rather more sophisticated stones have also been found. These are usually rectangular blocks, markedly different from the centurial stones, which are ordinary building stones with tails. One example, now alas lost, is dated to AD 158 and refers to the rebuilding of the Wall. On another, the word perfecit (which has meanings including ‘finished’, ‘perfected’, and ‘achieved’) is used, suggesting that the Wall was in the process of being completed.
Various interpretations are possible. Perhaps after the advance into Scotland c.AD 140, much of the Wall was demolished. Certainly, the gates of milecastles appear to have been removed and the Vallum, the great earthwork behind the Wall, was slighted, with gaps cut in the mounds and material thrown into the ditch to create crossings every 40m or so. But would the army go to the trouble of perforating the Wall in similar fashion? Nick Hodgson has argued that the inscription suggests that the army was bringing to completion or perfection something which had already been begun but not finished, or which required limited work to bring it to a state of service.
There is yet a third possibility. Hadrian’s Wall was of simple construction: facing stones set in mortar held in place a core of earth, clay, and stones. It was an inherently unstable structure and, in the two decades that Hadrian’s Wall was abandoned, it is possible that it had deteriorated sufficiently to require significant repairs. Excavations by the Tyne and Wear Museums and Archives team at Wallsend revealed several collapses of the Wall, though here the problem was that it had been undermined by the flow of water through a small valley that the Wall had to cross.
So, was Hadrian’s Wall finished at the time of Hadrian’s death? The un-dug ditch and partially completed upcast mound, the lack of an outer ditch and granaries at Birdoswald, and no Military Way indicates that it was not. This evidence also receives support from the scale of the building work that had to be undertaken when the army returned from the Antonine Wall in the 150s or 160s.
Should we be surprised if Hadrian’s Wall was not finished by AD 138? There is growing evidence from other frontiers of the Roman Empire that their construction was a time-consuming and lengthy task. Analysis of coins suggests that the building of the Upper German frontier occupied most of the period from AD 105 to 115. At about the same time, troops were building a new road known as the Via nova Traiana along the frontier of the newly absorbed province of Arabia. The construction of the road itself, never mind the military installations along it, took the best part of a decade. Moreover, examination of the phasing and dating of the building of the towers and palisade on the frontier in the province of Raetia (in modern Bavaria) in the 160s suggests the work there took at least seven years.
Roman frontiers were major engineering works. We should expect them to have taken a long time to construct. What we rarely take into account in trying to compute the length of time the projects took to complete is that the soldiers had other duties to undertake, not the least of which was to obtain the supplies to keep them fed and watered (with beer and wine), armed, and clothed, all of which might have taken them away from the building projects for weeks at a time. We can only admire the perseverance of the Roman state that these projects were indeed finished at all.
Further reading Paul Bidwell, Hadrian’s Wall at Wallsend, South Shields (2018), £35, ISBN 978-1527229969. David Breeze, The Frontiers of Imperial Rome, Pen and Sword (2019), £14.99, ISBN 978-1526760807. Rob Collins and Matthew Symonds, Hadrian’s Wall 2009–2019, Kendal (2019), £15, ISBN 978-1873124826. Erik Graafstal, ‘Hadrian’s haste: a priority programme for the Wall’, Archaeologia Aeliana, 5th series, 41 (2012), 123-184. Nick Hodgson, Hadrian’s Wall: archaeology and history at the limit of Rome’s empire, Robert Hale (2017), £19.99, ISBN 978-0719818158.
All images: David Breeze, unless otherwise stated.