Exploring the extra-mural settlement of a Hadrian’s Wall fort
For the last three years, excavations outside the walls of Birdoswald Roman fort have been helping to characterise the community who lived in its shadow. Carly Hilts visited the site and spoke to Ian Haynes to learn more.
Banna – or, to use its modern name, Birdoswald – is one of the most intensively investigated forts on Hadrian’s Wall: some 21% of its interior has been excavated to-date, and Tony Wilmott, a Senior Archaeologist for Historic England, has been heading research on the site for more than 30 years. Rather less well-understood, however, is the Roman settlement that grew up outside the fort and which, at its peak, was twice the size of the military construction. In order to redress this balance, for the last three years Tony has been co-directing a project with Ian Haynes, Professor of Archaeology at Newcastle University (facilitated by English Heritage, which cares for the site), to help characterise how different areas of extra-mural occupation were used over time. The project’s penultimate digging season has now drawn to a close, and on the second-to-last day of excavation I joined Ian for a tour of the archaeology that had been uncovered.
This year’s excavations represent the largest expanse under excavation at Birdoswald since the 1990s, with trenches active to the east and west of the fort, as well as north of Hadrian’s Wall. One of the main focuses of the project remains Trench A, now in its third year. We first described its contents in CA 379, but to summarise here: in the 1930s, a brief excavation by Ian Richmond uncovered what he interpreted as the remains of a watchtower surviving to a height of 13 courses of huge stone blocks. Richmond had to abandon his investigation when he hit the water table and the trench flooded, but since 2021 Ian and Tony have been bringing the remains to light once more. They quickly established that this was no watchtower – Richmond’s ‘square’ structure is, in fact, rectangular, and it sits in a gully that would have defeated any purpose of observation. Instead, last year they found box-flue tiles, stacks of pilae – the distinctive pillars of a Roman underfloor heating system – and quantities of ash and red burnt material within the soil. This is no watchtower: it is a bathhouse.
It would have been only part of a much larger bathing complex, which geophysics suggests lies immediately to the east, but it was nevertheless clearly an impressive building, imposing in scale, with finely worked masonry. Since CA’s last visit to the site, the team have uncovered further features relating to its function, including the heating channel from the praefurnium (furnace), containing deposits of soil thick with ash. By analysing this, they hope to find out more about the fuel that was being used, whether it had been locally sourced or brought from elsewhere and, if it is local, what it can tell us about the surrounding environment. The present excavation has also revealed the iron bars that would have been used to support the large boiler tank (very rarely found in situ; the closest parallel is at Pompeii), as well as stone blocks with carefully bored holes that would have accommodated (probably lead) pipes that have long since been stripped away and reused elsewhere. These complement 2021’s discovery of iron collars that would have once secured long-decayed wooden pipes channelling water to the site.
Some elements of how the bathhouse functioned, though, are less easy to interpret. Ian highlighted some ‘interesting engineering’ thought to relate to the praefurnium, where a wall had been hollowed out to create spaces inside it – to channel what, and what it was feeding into, is still unclear, but the structure is clearly more complex than previously thought, and it is hoped that this may become clearer during next year’s excavation.
The structure’s afterlife is equally intriguing. Ian and Tony believe that it would have originally been built in the early 2nd century – provision of a bathhouse would have been a priority once the fort was up and running – but what happened when it went out of use? Spot-dating of finds suggests that the building was abandoned in the later 3rd century, like the rest of the extra-mural settlement, and it was previously thought that the structure and its surrounding gully had been quickly backfilled to ameliorate the security risk posed by a large empty building obscuring the view from the fort (and providing a convenient hiding place for attackers). Now, though, there is emerging evidence that the building had continued to be used for some time after its original function ceased.
‘When you stop heating a Roman bathhouse, you are left with a building with many large halls,’ Ian observed. The team believe that the structure was subdivided in its later life, while there is a holloway running around its side, giving access to the building – and someone later repositioned a windowsill to create a handy step down into it. ‘Someone was still finding it useful to access this space,’ Ian said. Precisely what they were accessing the building for, however, remains a mystery, though one possible clue emerged early in the project: in our feature from 2021, we described the discovery of possible grave-cuts dug through the floor of an adjoining room. Might this eye-catching building have been repurposed as a grand mausoleum?
EVIDENCE OF INDUSTRY
Elsewhere on the site, the other two trenches that we covered in CA 379 – Trench B, which explored a strip house located on the north road out of the fort, and Trench C, which searched for defensive features north of Hadrian’s Wall – have been closed, but Trenches D and E have illuminated a host of different perspectives on what life was like in the extra-mural settlement.
Located north of the Wall, Trench D has been expanded since last year as the team continue their exploration of the road linking Birdoswald to the outpost fort at Bewcastle, and any structures associated with the route. It is a trench that has proven rich in finds, with last year’s excavations yielding artefacts including pottery, hobnails, and intaglios made of glass and jasper, lost from rings that would have been used to seal documents. This year they have been documenting the remains of timber structures – drainage gullies and the foundation platforms that were formed from the soil upcast from these ditches – that were all contemporary with the fort. This part of the site has yielded a wealth of evidence for the community that inhabited them: lots of everyday eating and drinking vessels, as well as imported Samian ware, and echoes of industrial activities including little drops of lead, glass waste, grinding tools, and evidence of simple metalworking (slag, signs of recycling/repairing metal tools), but nothing as complex as smelting.
Even more extensive, though, are the finds that have emerged from Trench E: a new, ambitious sweep of excavation measuring some 60m by 10m to the west of the fort. This investigation was opened because of intriguing geophysical survey results: they showed the presence of a road that appeared to have been dramatically widened at one point along its route. ‘If this was a medieval town, it would be an obvious marketplace space, but how should we read it here?’ Ian said. The team duly set out to learn more.
Sure enough, the road surface can be seen running through the centre of the trench, but the surrounding archaeology has far exceeded expectations of what the team might find. This includes a pale strip running beneath where the fort now lies, representing the remains of the original turf line of Hadrian’s Wall before it was rebuilt in stone further to the north. It is the widest stretch of the Turf Wall uncovered in living memory, Ian said, and its preservation is illuminating: you can clearly see its ditch, still filled with blocks of turf that were tipped into it when the wall was slighted. After the ditch had been backfilled, the road was then built over its counterscarp (the material thrown up on the outer side of a ditch to make the obstacle even deeper), which provided a convenient camber. The Roman builders then only had to add river cobbles to its surface and dig drains on either side to create a serviceable routeway in double-quick time.
Just as the geophysics had suggested, the road is noticeably wider in the central part of the exposed section, with a lot of redeposited natural material increasing its span. The resulting surface is certainly broader than you would expect for a road, Ian said, though it is not yet certain whether this widening was deliberate or the result of natural scouring down the slope; if it was deliberate, its purpose remains obscure. This is something that the team hope to clarify next year.
This is an extract of an article that appeared in CA 402. Read on in the magazine or on our new website, The Past (click here to subscribe), which details of all the content of the magazine. At The Past you will be able to read each article in full as well as the content of our other magazines, Current World Archaeology, Minerva, and Military History Matters.