Forts, castles and camps

We are starting at Bewcastle Fort around 10 kilometres north of Hadrians Wall – well that’s as the crow flies. But then we will be returning the Wall and some of its most dramatic landscapes and archaeology. From a ruined medieval Thirlwall Castle near Greenhead village – built completely of re-purposed Roman stones – we climb up onto the escarpment of the Whin Sill – 295 million years ago it was an intrusion of molten rock that then solidified into a hard rock called dolerite. It resisted erosion by 1000m thick ice sheets and stands proud as one of the rocky icons of the northern landscape. 

Transcript

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Episode three forts, castles and camps. We are starting around ten kilometers north of Hadrian's Wall, well that's as the crow flies, but then we'll be returning to the wall and some of its most dramatic landscapes and archaeology. From a ruined medieval Thurwell castle near Greenhead village, built completely of repurposed Roman stones, we climb up onto the escarpment of the windsill. Two hundred and ninety five million years ago it was an intrusion of molten rock that then solidified into a hard rock called dolerite. It's resisted erosion by even one thousand meter thick ice sheets and stands proudly as one of the rocky icons of the northern landscape. Moriture te salutant, roughly translated and not well spoken, those who are about to walk, we salute you. A seasoned wall walkers will tell you, you'll love the Windsill Ridge for the incredible views it gives. This is wall country on steroids. Your thighs may like it a bit less for all the ups and downs, but just think of the muscle tone you've gained. There is a Roman road that goes from Bird Oswald Fort to our next stop. Bucastle Fort. Its line is very straight, very much as our crow flew, and it is marked on the Ordnance Survey map in places, but if you choose to hike there, you might struggle to find it. Bucastle today is a small, quiet, dispersed settlement in the valley of the Kirkbeck. It is centered on a small, flat topped hill of sand, outwashed from the melting of the last ice sheet. Surrounding it to the north, east and south are high, rough fell land of repeating horizontal layers of sandstone, limestone and shale, dating back from the oldest part of the Carboniferous period three hundred and fifty million years ago. The well drained sand hill in the valley must have been an attractive site for the earliest prehistoric settlers, and it is said there was a shrine to Corcidius, a local god here. Around AD one hundred two a Roman legion built an earthen wood fort at Bucastle at the end of the Maiden Way, the road which connects it to Bird Oswald. Stone signal stations on prominent sandstone scarfs at Baron's Pike and Gillile's Beacon provided vantage points for the fort and the road. At least two auxiliary cohorts were garrisoned at Bucastle, the Dacians from Romania, Bulgaria and Serbia, and the Nervii from Belgium. From artifacts found on the site, they adopted Cochidius as their god too, and the Roman name of the fort links to that Phanum Cochidiae. Over the next two centuries the fort would be rebuilt in stone, its walls defining an almost hexagonal perimeter mirroring the plateau. Possible sources of building stone are the quarries at Crossgreens in the north, and one in the aptly named Earthwork Sandstone. The fort has a turbulent history and was destroyed and rebuilt several times, finally being abandoned in the fourth century. In the centuries that followed, Bucastle continued to draw people. It became an Anglo Saxon settlement, and in the churchyard is a richly carved stone cross shaft dating from the late seventh or early eighth century. The cross, one of the finest to survive in Britain, may well have been made from stone robbed from the Roman fort, but there are also so many primary sources for such rock that in the thick older sandstones that surround the village. The thirteenth century church, St. Cuthbert's, has much repurposed Roman stone too. The Vikings were here, and the modern name of the village may derive from Buth, a Norse chieftain. Sometime after the ten ninety two annexation of Cumberland from Scotland, Bew Castle was built in the northeast corner of the Roman fort, largely from its stones. The castle's position on the front line meant it was a busy place during the wars between the Scots and the English, and it was also rebuilt multiple times. It was garrisoned for the last time in sixteen thirty nine to deal with commotions in Scotland, and dismantled by parliamentary forces in sixteen forty one. Visit Bewcastle. You may have all this history and the stones that tell it all to yourself. There's a Roman fort at the start of the Winsill Ridge. It's called Magna or Cavoran. There is a Roman Army Museum there too, and for the last couple of years there have been excavations at the site. One of the prime reasons is to understand what is happening to the condition of the ground that holds so many artifacts. Climate change is thought to be responsible. The discovery and preservation of archaeological remains often seems to be serendipity, but we now understand much more about the reasons why they survive in some places, but not in others. Artifacts found on land are usually in ground that humans have disturbed, whether in life or in death. Sometimes that zone extends down into natural geology, quaternary deposits, or maybe even bedrock. But mostly objects stay within relatively shallow surface layers, the soil and the subsoil. These surface layers commonly inherit many of their characteristics from the geology beneath, at its most basic, whether they are acid or alkali. If you look at a soil map, you will see that it mimics a geology map. Other factors do come into play, for example, the water table and subsequent human interference. How well different archaeological remains survive depends on the properties of the material they are found in, the way their physical and chemical composition reacts to their place of burial, and how land use changes like agriculture, development and changes to the groundwater system impact the area. Acid soils preserve pollen well, but are detrimental to metals, bone and teeth, which all survive longer in alkali conditions. Everything is better preserved when oxygen is excluded, in other words, in anaerobic waterlogged ground. This environment conserves deposits like leather, clothing, wood and plants. Such sites are rare in many parts of Britain, but the north of England is blessed. The acidic and wetter conditions found in places here mean that while bone shells and ferrous and copper metals are often poorly preserved, invaluable organic deposits survive much better. The fort at Magna is an excellent example of archaeological preservation and its challenges. Thought to have been established as a Staingate Fort around AD eighty, it was developed into a fort on Hadrian's wall and was occupied until the end of Roman Britain. It is on the junction of two Roman roads, and recent geophysical surveys have indicated extensive settlements around it. There may have been as many as five hundred soldiers at different times from Syria and Dalmatia, and many more supporters and civilians. Some preliminary investigations fifty years ago found timber remains under a stone gateway. Twenty years later, within deep anaerobic conditions, Roman leather was encountered. Between the fort and the wall today is a peat bog. It may have been a lake in Roman times. It was sufficiently large, deep and wet enough to persuade the diggers of the Vallam to divert their ditch. Its kinks are obvious on a map. The peat bog is no longer obvious, but it was to geologists in 1879, and they included it in their first map of the area. They also delineated glacial deposits and the windsill and limestone layers beneath those. Such geological factors are critical to any hydro environmental assessment of an archaeological site. This bog is now drying and shrinking, and the topography around the fort is changing. Magna's 17 hectare scheduled monument is considered likely to contain rare anaeroic conditions comparable to those found in Winderlander and Carlisle, places which produce stunning discoveries. Areas of organic preservation at Magna are believed to be at serious risk, and a five-year programme of excavation and research on the changing environment started in 2021. As we continue east, we pass a gaping hole in the ground, and in Hadrian's Wall. As it has quite a bit of interest to us geologists, it would be remiss of me not to tell its story. Wall Town is a huge restored old quarry in the Windsill. The quarry opened in 1876 and closed in 1976. The windsill, windstone to quarrymen, dollwright to geologists, is so hard that they had to use explosives to blast it from the rock face. Its hardness meant it was perfect for roadstone chippings used in tarmac, and a century ago it was also used for sets for cobbling streets. The windsill was once molten magma. It was injected from deep in the earth in between the layers of Carboniferous limestones, sandstones and shales, and then it cooled, solidified and contracted, forming its prominent vertical cracks and fissures. Millions of years of erosion since have left the hard dolerite rock ridge standing proud, until it, and the section of Hadrian's wall that ran along it, was quarried away. The enormous hole that was quarried out was infilled with compacted stony clay as part of its restoration. Slowly nature is returning, and there is now a wide assortment of plants on the varied soils and rock faces of the quarry. Look out for common rock rows on the thin wind soils. On the quarry floor are common spotted orchid and northern march orchid and their vigorous hybrid, with numerous sedge species. We're about five kilometers east and just hiked past another disused windstone quarry, Corfields. This one also removed a whole section of Hadrian's wall. It is a deep hole filled with water now, and the lake and the dramatic eastern quarry face, cutting across the column adjointed wind escarpment, is a honeypot for photographers, day and night. Geologically, the route the Romans chose for their wall across the Solway Tyne Ismoths makes perfect sense. The placement of some of their mile castle and turrets less so. The terrain is the dominant influence on the line of the wall, and it is geology that shapes the terrain. In the central sector, Hadrian's wall takes advantage of the escarpment of the windsill, while the sectors extending to the west and east coasts occupy the highest ground with good views south. But although the wall heeds the shape of the ground, other elements of the frontier infrastructure appear less sensitive to it and the underlying rocks. The current thinking is the wall line was laid out on the ground by legionary surveyors, and the positions of the mile castles and turrets were staked out along the line at spacings predetermined by a plan devised remotely at a much higher level. There are eighty mile castles, double gated fortlets with fortified gateways, one approximately every Roman mile, with two turrets between each pair of mile castles. Milecastle forty two, just east of Hole Gap and Corfield's Quarry, may be one of the most photogenic mile castles on the wall, but its position seems less than practical. It's built on a steep slope, and its northern gateway is a few meters short of the north scarp of the windsill. The slope in sight would not have made the builders' lives easy. It does not seem like the best trade-off, but one theory is the mile castle was moved from its original stake position in Hole Gap, so that its occupants could maintain visual contact with the Holt Whistleburn Stain Gate Fort. But a more fundamental factor comes into play, one that affects multiple aspects of the interpretation of the Frontier's installations. The reliability of Roman wall measurements. The standard mile is a thousand paces, fixed as five thousand Roman feet or one thousand four hundred and eighty-one meters in twenty-nine BC. Along the wall, distances between milecastles vary, most widely, understandably, in the seriously undulating central zone. The Romans probably used stakes and a rope to survey and measure. As an experiment, mapping software was used to emulate the original rope measurement on just one of their miles. This calculated the distance between milecastles forty one and forty-two as 1,644 meters, an increase of more than 10%. Corfields is certainly not alone in its apparent insensitivity to both terrain and the perceived rigidity of the plan. Whether the builders of Hadrian's Wall were influenced by the original master plan, by an emperor's revisions, by adoption of rigid stone walls and not flexible turf and timber, and not least by the terrain and its rocks, is a puzzle that is not going to be solved easily. To finish, I brought you downhill, off the windsill escarpment and the wall, and to the twice brewed pub and brewery. What better way to end an episode? While you try the Sycamore Gap bitter, though I prefer the Gallia Pale Ale, go out into the garden at the rear and across the little stream. In a field on the other side of the stream is archaeology. See it? No, I thought not. In parts of Scotland, Wales and the north of England, low banks of earth in the shape of rectangles can with difficulty be spotted in the fields. South of the central sector of Hadrian's wall they seem to be everywhere. Roman camps don't look much, for almost two thousand years most of their earthworks have spread, and they are now just low linear mounds. The one immediately south of the twice brewed inn is just like that, and so is best seen when the sun is low and the shadows are long. Then you can pick out the ramparts and the gateways, often guarded by additional defences. The influence of the underlying geology on temporary camps like these is not that significant, although you don't see many where bedrock is at surface, like the steep southern dip slopes of the windsill dolrite and sandstone escarpments. The builders of these temporary camps seem to prefer to locate them on softer ground, glacial stony clay. They sensibly avoided what are now wet peat bogs, which may have been lakes back then. Many camps are close to roads like the stainate. That's logical, as soldiers prefer to march on a firm base. The mounds seem to have been dug or scraped up from the exterior, leaving a complementary ditch, and together these may have produced a rampart originally around one point five meters high. There is little detail on their construction, as very few modern excavations have been done. Roman military manuals advised that they should be built with their front facing the enemy and their rear close to the crest line to avoid dead ground. Many camps are on slight slopes, not ideal as those of us who have slept in tents will testify, but a strategically defendable site, not comfort, was the priority. That overriding factor, a safe position and perimeter, also means that the size of the camps does not necessarily relate to the numbers of soldiers they contained, a topic of archaeological debate for a long time. The camps vary considerably in size. Seatsides I camp, less than four hundred meters south of the Twice Brood camp, is over six point seven hectares in area. That's two hundred and fifty-two by two hundred and eighty-two meters. It and its near neighbour, Seatsides II, could have held many thousands of men. In contrast, four hundred meters southeast of Seatsides I, beside the road to Barden Mill, is a camp which measures barely twenty-five by twenty five metres. The size of these smallest camps may well indicate their purpose. Troop training, army habits do not change. But the function and dates of the larger camps have been less easy to establish, and much conjecture surrounds them. Some will undoubtedly have been for construction of the wall and its infrastructure, but arguably the majority were built by army units on manoeuvres. I hope you did manage to pick out the subtle ramparts and are enjoying your virtual beers in the virtual sunshine. If you could look up to the farm on the hill to the south, you might have seen a geologist bent over his laptop, trying to persuade more people to love rocks. You might have even sat beside him in the pub. He does take a break sometimes. And if one day you get to visit, you could also drop into the National Park Visitor Centre, aptly named the Sill, and buy one of his signed rock books from the lovely people there. Make the most of the evening. Next time we are heading back up the hill you just walked down.