The documents tell a story that is a good deal more consistent than Blake and Lloyd suppose. The story they tell is more consistent if we allow that the texts that have survived from the past are interpretations of events, the results of people writing many years after the events they are describing and trying to understand those events. It is unfair to these writers to treat their texts as sacrosanct and to regard their statements as beyond criticism. Only by understanding why a particular author wrote what he did can we hope to get back to the events behind the words. Too many writers in the mould of Blake and Lloyd assume that if a text states something as a fact, then it must be either right (as they believe for the Brut y Benhinedd) or wrong (as they believe with Geoffrey of Monmouth’s placenames). It does not seem to occur to them that ancient writers can make mistakes.
An analysis of claims for ‘Severus’s Wall’ must begin with the earliest text. This is Aurelius Victor’s Liber de Caesaribus, published in 360. He states (xx.18) his maiora aggressus britanniam, quo ad ea utilis erat, pulsis hostibus muro muniuit per transuersam insulam ducto utrimque ad finem oceani ‘On top of this, attacking Britain and repelling the enemy, he fortified it, insofar as it was useful to it, with a wall across the width of the island, to the bounds of the ocean on both sides.’ The text is not specific about where in Britain Severus built his wall, except that it ran across the width of Britannia, implying an east-west alignment (Roman maps had north at the top, in the modern manner). Aurelius Victor is the first writer to claim that Septimius Severus built a wall in Britain, over 140 years after that emperor’s death; he is vague about the details and we do not know what his source of information might have been.
Nine years later, Eutropius’s Historiae Romanorum Breviarium (viii.19) supplies additional data, without appearing to derive directly from Aurelius Victor: nouissimum bellum in britannia habuit, utque receptas prouincias omni securitate muniret, uallum per cxxxii passuum milia a mari ad mare deduxit, ‘he had his last war in Britain, and to fortify the conquered provinces with all security, he built a wall for 132 miles from sea to sea.’ Here we see an absolute figure given for the length of the wall. Writing almost 160 years after the death of Severus, Eutropius is only the second writer to credit him with the construction of a wall and the first to give details of its length.
The next text to mention ‘Severus’s Wall’ is the Historia Augusta. Although it claims to be the work of six separate authors writing under Diocletian or Constantine (i.e. 285×334), there is ample evidence that they are the product of a single author, writing in the reign of Theodosius I (379-395). Computer analysis has shown that the texts cannot have been written by different individuals, while entire sections (in the lives of Marcus Aurelius and Septimius Severus) have been taken bodily from Aurelius Victor and Eutropius. It is in one of these sections (Severus xviii.2) that the statement about Severus’s Wall is to be found: brittanniam, quod maximum eius imperii decus est, muro per transuersam insulam ducto utrimque ad finem oceani muniuit, ‘He fortified Britain, which is a great ornament of his reign, with a wall led across the breath of the island to the edge of the Ocean on both sides.’ It shares a large number of words with Aurelius Victor, from which it is clearly derived. We cannot use this passage as evidence that the author of the Historia Augusta knew of three walls in Britain, simply that, having mentioned walls built by Hadrian and Antoninus Pius, a source that he plagiarised mentioned one built by Severus, and he was in no position to contradict the source.
St Jerome’s translation of the Chronicon of Eusebius adds the passage from Eutropius almost verbatim, while Orosius’s Historia adversus paganos (vii.17) appears to use both Eutropius and Jerome. Gildas knew Orosius, but his account (de excidio et conquestu britanniae chapters 14 and 18) of the Roman walls is very complex and very muddled, but still allows only two walls, one of turf and the other of stone. Both are misdated to the late fourth and early fifth centuries. Bede then knew both Gildas, whom he copies as his only source of information for the fifth century, thus giving the two post-Roman walls (Historia Ecclesiastica gentis Anglorum i.12), but he was also familiar with Orosius, so he gives the account of Severus’s Wall (HE i.5). He was a careful historian, though, and aware of the problem he has created, so he sets out to correct the impression that Severus was responsible for building the stone wall: non muro, ut quidam aestimant, sed uallo distinguendam putauit. murus etenim de lapidibus, uallum uero, quo ad repellendam uim hostium castra muniuntur, fit de cespitibus, quibus circumcises, ‘not with a wall, as some guess, but with a rampart; for a wall is built with stones, but a rampart, with which camps are fortified to repel the force of enemies, is made with turves.’ It is likely that Bede, as a native of Jarrow, was familiar with Hadrian’s Wall and the so-called vallum to its south, and assumed that the stone wall was built as a replacement for the earthwork vallum; having learnt from Gildas that the stone Hadrian’s Wall was a product of the fifth century and that the turf Antonine Wall was late fourth- or early fifth-century, he concluded that the vallum must be the defensive work built by Septimius Severus. His explanation of the difference between uallum and murum is entirely his own, but it suggests that he had seen not just Orosius, who writes of a uallum but also one of the earlier writes such as Eutropius or Aurelius Victor, who mention a murum, wrongly, according to Bede. The Historia Brittonum (Chapter 23) uses the same data as Bede, but whether the author got the information directly from Bede or from one of the earlier writers (he certainly was not using Gildas here) is not clear. His statement murum et aggerem a mari usque ad mare per latitudinem brittanniae, id est per cxxxii milia passuum deduxit, et uocatur brittannico sermone guaul, ‘he built a wall and rampart from sea to sea across the width of Britain—that is, he took it across 132 miles—and it is known as Gwawl in British speech’ adds a local detail, that it has a vernacular British name. This name derives from Latin uallum and suggests that it was the term used locally to refer to the structure.
We thus have an entire history of Latin texts that are not independent witnesses to the building of a wall by Septimius Severus, but which go back to Eutropius, writing in 369; he may have rewritten the sentence in Aurelius Victor that is the first (that we know of) to make the claim that Severus built a wall in Britain. We do not know where Aurelius Victor got his information.
What of the figure of 132 miles? It is remarkably stable in the textual tradition, being quoted in this form from Eutropius onwards. Latin numerals are open to corruption (as can be seen very clearly in the confused textual history of the Historia Brittonum. The figure cxxxii given originally by Eutropius does indeed mean 132 miles. Roman numerals were, however, subject to a number of common confusions. In manuscripts, u is often miscopied as ii, x as u, c as l and vice versa for all instances. If Eutropius had misread an unclear l as c in his source of information, we would be confronted with a wall lxxxii (in other words, 82) Roman miles long; Hadrian’s Wall is 80 Roman miles long.
We do have two almost contemporary histories that cover the reign of Severus: the Greek authors Cassius Dio Cocceianus and Herodian. The work of Dio (the ‘Iστωριαι ’Ρωμαναι) ran as far as 229, the year in which he held his second consulship, but most of the text is lost and portions only survive as an Epitome Dionis Nicaiensis made by the Byzantine scholar Ioannes Xiphilinos in the eleventh century. This is unfortunately the only version we have of Dio’s account of Severus’s British wars. However, from Xiphilinos (Epitome 321) we learn that Severus campaigned against the Καληδόνιοι and the Μαιάται, the latter of whom lived ‘near the wall dividing the island in two’. Herodian, whose History of the Empire from the time of Marcus, written c 238, also locates Severus’s campaigns in northern Britain and mentions (iii.14) that they took place ‘once the army had crossed the rivers and earthworks on the frontier of the Roman empire’, clear reference to the two existing defensive barriers. He does not mention the construction of any new earthworks or walls. It is possible that a later, less careful writer mistook Dio (whose actual words we do not have) or Herodian as saying that Severus had built one or other of the walls he is said to have crossed.
We still have the rather bizarre account of Prokopios (or Procopius). He wrote several histories of the wars conducted by Justinian, which were eventually combined into a single book, leading to a confusion of titles. The original work, de bello Gothico (‘About the Gothic War’) was incorporated into de Bellis (‘About the Wars’), with Book IV of the former work (which includes the description of the island of Βριττία, taken to be Britain, although the usual Greek word is Βρεττανία) becoming Book VIII of the combined work. His description of Britain does not inspire a great deal of confidence in his knowledge of the place.
He writes: ‘in this island of Brittia, the men of old built a long wall, cutting off a large part of it, and the air and the soil and everything else is not alike on the two sides of it. For to the east of the wall, there is healthy air, changing with the seasons, moderately warm in summer and cool in winter, and many men dwell there, living in the same way as other men, and the trees are rich in fruit which ripens at the appropriate season and the crops flourish as well as any others and the land seems to boast of its abundance of waters. But on the west side, everything is the reverse of this, so that it is impossible for a man to live there for half an hour, but the viper and countless snakes and all kinds of other wild creatures occupy the place as their own. And, strangest of all, the inhabitants say that if any man crosses the wall and goes to the other side, he dies straight away, being quite unable to bear the pestilential nature of the air in that region, and likewise death meets and overtakes wild animals that go there. Now since I have reached this point in my story, I must relate a rather fabulous story, which did not seem at all trustworthy to me… They say that the souls of the dead are always conducted to this place.’
It is very difficult to know what to make of this. Prokopios is evidently very poorly informed about Britain, as there is nowhere a wall that separates part of the island with good air from part with bad air, whether it be Hadrian’s Wall, the Antonine Wall or Offa’s Dyke.