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The Last Roman Emperor to Campaign in Britain

Roman Britain had its fair share of imperial visits during its 350+ year existence. Without taking into account the numerous usurpers that the island spawned (or helped to) – Clodius Albinus, Carausius, Allectus, Constantine I, Valentinus, Magnus Maximus and Flavius Victor, Marcus, Gratianus, Constantine III and Constans II, several legitimate emperors did pay a visit to Britain.

 

Claudius travelled to the island in the aftermath of the conquest he had initiated in AD43; Hadrian arrived on the island in 122 during his tour of the empire, when he initiated the building of the wall that bears his name; Septimius Severus campaigned against the Caledonians in 208-211, accompanied by his sons, Caracalla and Geta, who succeeded him when he died at York; Constantius I also campaigned in Britain, first against the usurper Allectus in his role of Caesar in 296 and then against the Picts in 305/306. He too was ‘succeeded’ by his son after dying at York, but the elevation of Constantine I was not exactly official. And even when Constantine visited Britain again in 307, it would appear that he had yet to receive any definitive recognition of what was still technically a usurped title.

 

Other emperors are known to have visited the island before their imperial elevation – serving as legate of Legio II Augusta, Vespasian took part in the invasion of Britain in 43, while the future Theodosius I accompanied his father to Britain to campaign against the so-called ‘Great Conspiracy’ in 368-369 (they also defeated the aforementioned usurper Valentinus). It could be that some other future emperors visited Britain in the years before they came to power as members of military or political entourages.

 

However, the last known visit to Britain by a legitimate serving Roman emperor (**there is a significant caveat to this declaration that will be addressed below**) took place nearly 70 years before the supposed end of Roman Britain in 411. The visitor in question was the youngest son of Constantine I, Constans (337-350).

 

We are somewhat fortunate to have three separate sources who mention this visit to Britain in 343 - Firmicus Maternus, Libanius and Ammianus Marcellinus. Unfortunately, the nature of these sources in either their genre or the condition in which they have survived greatly hinders our knowledge of why Constans travelled to Britain and what he did during his visit.

 

Julius Firmicus Maternus’ De errore profanarum religionum would seem to potentially be the most trustworthy due to its writing in around 346, only three years removed from Constans’ expedition. However, showing all the zeal of a recent convert, Maternus had gone from the author of a treatise in astrology – Matheseos libri octo (‘Eight books of astrology’) – in c.334-337 to a vicious anti-pagan, Christian apologist in little more than a decade. Indeed, such was this transformation that some historians of the 19th century could not reconcile that the author of Matheseos libri octo and De errore profanarum religionum were the same person. This means that rather than being any sort of historical work, De errore profanarum religionum is a scornful critique of pagan practice, which in its treatment of the Christian Constans is eager to present him in the best light possible. This makes Maternus’ mention of Constans’ British campaign exaggerated and lacking any real detail.

 

The Antiochene pagan scholar, Libanius, may have written hundreds of rhetorical exercises, speeches and letters, but it is his 64 Orationes that are of interest here, specifically Or. LIX, which focuses on the careers and achievements of Constantius II and Constans (Dodgeon in Lieu and Montserrat (1996) 164-205). While not strictly a panegyricist, there is perhaps just enough praise from Libanius to provide some doubt over the exact extent of Constans’ achievement. Furthermore, Libanius’ record of Constans’ British campaign contains far less detail than we would like.

 

The genre issues of Maternus and Libanius would seem to pale into insignificance when we have some record of Constans’ British campaign from Ammianus Marcellinus, the pre-eminent Roman historian of the fourth century. However, unfortunately, Ammianus’ extended record of Constans’ dealings with Britain are contained within the books of his work that are now missing. And when, on two occasions, Ammianus mentions the British campaign of Constans in his books that do survive, he is true to his classicising style in being uselessly brief, summing up the crossing of the English Channel in less than perfect sailing conditions as something “Constans once did (as I have told)” (Ammianus XX.1.1) and explaining how “I have thought it superfluous to unfold again what has once been set forth, just as Homer's Ulysses among the Phaeacians shrinks from repeating the details of his adventures because of the excessive difficulty of the task.” (Ammianus XXVII.8.4)

 

One other source of information for the British campaign of Constans is the Codex Theodosianus. This is not because of the content of any of the laws Constans passed, but the date and location of where they were issued. This can give us useful information about where Constans was at certain times, which as will be seen can give a layout of the chronological duration of the British campaign, or at least Constans’ presence on the island.

 

We know from CTh IX.7.3 that Constans was present at Milan on 4 December 342, which is where it might be thought he planned to spend the winter of 342/343. However, not even 8 weeks later, Constans issued CTh XI.16.5 (cf. CJ III.26.6) on 25 January 343 from Bononia, modern Boulogne-sur-Mer in northern France, marking his presence on the English Channel.

 

It is not clear if Constans’ presence at Bononia on 25 January 343 was on the outward or homeward journey. The contents of that law would not seem to help any with the exact imperial circumstances of its issue beyond the place and date. From Firmicus Maternus, De errore profanarum religionum 28.6, Libanius, Or. LIX.137-140 and Ammianus XX.1.1, we can merely ascertain that Constans crossed the Channel in winter, a considerable feat in itself, but nothing more in terms of date.

 

Constans was definitely back on the Continent by 30 June 343 to issue CTh XII.1.36 from Trier – so whether the law from Bononia was on the outward or homeward journey, this was not an extensive years-long campaign such as that of Septimius Severus. But is it to be measured in months or merely weeks?

 

With the lack of definitive information from the sources, we must look at other avenues for inferences on how long Constans might have been in Britain. One such avenue is travel times in the ancient world. An immense amount of work has gone into calculating travel times across the Roman Empire in the ORBIS project at Stanford (it is well worth a look – https://orbis.stanford.edu/). This can give some idea as to whether Constans’ presence at Bononia could be part of the homeward voyage or not.

 

It suggests that in the height of winter, with cost being no option to the emperor and all the military channels open to him, it would take at least 19 days to travel the 1,000+ km from Milan to Bononia (a horse relay would be much quicker, but Constans will have needed protection and an army for his crossing to Britain). The crossing of the Channel and then moving to the British provincial capital at London would have taken another 3 days. This would suggest that the very earliest Constans could have made it to London from Milan would be around Christmas Day 342 if he left straight after the publishing of CTh IX.7.3 at Milan on 4 December 342 (a supposition for which we have no evidence).

 

The lack of information about what Constans did in Britain does not help matters with regards to even a vague chronology. The seeming rapidity of the ‘quelling’ of any disturbance could suggest that it had abated even before he arrived, reducing his British ‘campaign’ to little more than a flying visit, with Constans visiting some troops, distributing some financial largesse and then returning to Gaul. Even if it said that Constans did not arrive in Britain until the New Year of 343, such a flying visit would make it possible that his presence in Bononia on 25 January 343 was after his British trip.

 

Possible but perhaps not altogether likely. Such a chronology would require not only a flying visit to Britain but also a lightning organisation and advance through Gaul that an imperial retinue and army was probably not capable of or at least willing to undertake, particularly in winter.

 

And if Constans’ British campaign was more than a flying visit, the possible timeline becomes even tighter. Any journey to a trouble spot outside of the south-east would add many more days to the chronology – for example, the journey to Hadrian’s Wall would be at least 9 days in one direction, with the return journey to Bononia taking at least 12 days.

 

Journey Leg

Days

Milan to Bononia

19

Bononia to London

3

London to Hadrian’s Wall

9

Hadrian’s Wall to London

9

London to Bononia

3

TOTAL

43

 

Therefore, a departure from Milan on or just after the 4 December 342 on a journey to Hadrian’s Wall and then back to Bononia will have taken a bare minimum of 43 days’ travel, could have seen Constans arriving back in Bononia in mid-January. And Maternus does intimate that the arrival of the emperor in Britain was “unexpected”, which could hint at his speed of arrival, rather than just the sheer novelty of an imperial presence in Britain (the island likely had not seen an emperor in 35 years, although other areas of the empire will have had much longer periods without an imperial visit).

 

However, this not only requires the most organised and rapid advance by Constans and his retinue, but also no actual campaigning by the emperor while he was in Britain. Again, while this seems chronologically possible, it appears realistically unlikely. The likelihood remains that Constans issued CTh XI.16.5 at Bononia before he crossed to Britain.


There is another source of corroboration for Constans’ involvement with Bononia – a medallion. Recorded in the Roman Imperial Coinage as RIC VIII, Rome 338, this is the only known example of this commemorative bronze medallion.

 

While its minting in Rome does not provide solid evidence of Constans’ presence in Bononia, the reverse legend – BONONIA OCEANEN – can only mean the city now called Boulogne-sur-Mer. This is because of the three other towns called ‘Bononia’ in Roman territory – Bologna in Italy, Banoštor in Serbia and Vidin in Bulgaria, none of these are near the sea.

 

It is clearly Constans on the obverse – the legend reads CONSTANS P F AVG­ – and while he was in northern Gaul on several other occasions, there is no other record of him being in Bononia. Therefore, it is logical to connect the issue of this medallion with Constans’ involvement with Bononia (if not strictly his presence given its minting in Rome), an event we have corroboration for in the form of CTh XI.16.5.

 

The reverse image presents Constans in full military regalia, standing in a rowed galley (three rowers are below Constans), holding a spear and shield. On the prow of the galley is a Victory holding a wreath and a palm, while behind the emperor are standards, all symbols of military triumph.

 

Could the tower perhaps be a lighthouse? Possibly the one of the lighthouses of Dubris (Dover) or more likely the lighthouse of Bononia known as the Tour d’Ordre, built in c.39 on the order of Caligula (Suetonius, Gaius 46)? The latter lighthouse stood for nearly 1700 years before falling into the sea in 1644 due to coastal erosion.

 


While it could depict a victory that was thought inevitable but yet to come, given its minting in Rome, it would seem much more likely that is a commemorative medallion of an event that had actually happened – Constans had travelled to Britain from Bononia, won some sort of victory there and then returned to Bononia having ‘conquered’ not just whatever trouble brought him to Britain in the first place but also the wintery seas with his safe crossings to and from the island.

 

The source material can provide a decent chronology of Constans’ British campaign taking place between 4 December 342 and 30 June 343, and even some inferences of an even tighter time frame; however, they are not altogether clear on what exactly was the purpose of Constans’ winter dash north through Gaul and across the Channel to Britain. The risky winter crossing would seem to indicate that it is was thought that an imperial presence was required in Britain, and therefore that there was a significant problem that needed to be addressed.

 

However, neither Maternus nor Libanius mention a military campaign in Britain, which would suggest that if there was one, it was not of any great consequence. Libanius further postulates that if there was some kind of rebellion in Britain that spurred Constans into making the cold journey north through Gaul and braving the winter seas, it had either been dealt with before his arrival or quickly faded away when word of his surprise winter arrival spread, something which Maternus suggests – “the Briton has quailed before the unexpected visage of the Emperor” (De errore profanum religionum 28.6).

 

That Constans travelled with only 100 men rather than a full legion or army would seem to suggest that there was little real campaigning to do. However, it was a long-established Roman anti-rebellion policy to race any soldiers to the flashpoint as quickly as possible, regardless of how few they were – following the military maxim reputedly coined a millennium later by the famed Turko-Mongol conqueror, Timur the Great: Better to be on hand with 10 men, than absent with 10,000. But then if there had been a military victory or even just the suppression of a rebellion by Constans’ mere presence, it would be expected that Maternus and particularly Libanius would have made much, much more of it. And if Constans had signally failed to deal with any rebellion, it would be expected that other sources would have made something of it and there would have been more evidence of Britain potentially removing itself from central governmental control again.

 

Conversely, rather than a local rebellion, Ammianus Marcellinus seems to mention trouble from the Picts, Attacotti and Scots in connection with Constans’ crossing, but he is the only source to do so and despite his strong reputation as an historian, he was writing nearly 50 years after the event and may be influenced by future trouble with the Picts and Scots. Indeed, Ammianus is not completely clear if the British tribal trouble is in connection with the reign of Constans or that of Julian (Ammianus XXVII.8.4).

 

One thing that Ammianus is more clear about is that he felt that Constans’ crossing to Britain in winter was worthy of note, presenting it as a seasonal feat that even his great hero Julian was unwilling to undertake. As already mentioned, Ammianus likely went into more detail on Constans’ crossing and time in Britain in his books that are now missing.

 

Libanius and Maternus were also keen to play up the winter crossing of the Channel, not only due to the lack of a military victory to focus on but also because it was a feat worth highlighting. This focus may also be seen in the imperial propaganda of Constans’ own regime, specifically on the BONONIA OCEANEN medallion. As mentioned above, Constans appears every bit the military conqueror on this issue – regalia, standards, spear, shield, Victory. He also appears to be about to throw his spear at a figure swimming in the sea. While this could be connected to the military victory he claimed to have won, it is perhaps more likely that it is connected to his ability/willingness to cross to Britain in the dead of winter – a triumph over the Ocean itself, with this swimmer perhaps being the personification of the Ocean or the Channel. Maternus certainly incorporated such imagery into his recounting of the campaign: “you have trodden upon the swollen and raging waters of the Ocean. The wave of a sea already become almost unknown to us has trembled beneath your oars” (Firmicus Maternus, De errore profanum religionum 28.6). The BONONIA OCEANEN medallion could therefore be part of an imperial attempt to control the narrative of Constans’ British campaign in the same way that it clearly is in the pages of Maternus and even Libanius? Playing up his ‘victory’ even if there was not actually any fighting to take place after his arrival.

 

Indeed, Libanius intimates that the entire episode was something of a publicity stunt; Constans travelling to ‘deepest, darkest’ Britain just to say he had been there, following in the footsteps his illustrious father and grandfather, and undertaking a dangerous journey in the process. It would be entirely proper for Constans to want to show his face in Britain, distribute his largesse both in person and in the form of coins to the people and soldiery of the island. Britain was not initially part of Constans’ realm. Upon the division of the empire amongst the sons of Constantine in 337, Britain had been allocated to the eldest brother, Constantine II, only for control of the island (as well as the other western provinces) to pass to Constans after the death of Constantine II in 340 during an attempt to impose his political and military superiority on Constans.

 

It could be that Constans’ British visit was in part to present the Britons with their new ruler. He may not be recorded visiting other regions added to his realm through the death of Constantine II, such as Spain, but then the Iberian Peninsula had not seen any active rebellion or barbarian trouble within living memory at that point. Britain had hosted usurpation in the form of Carausius and Allectus, and Constans’ father and grandfather had campaigned in northern Britain a generation previously. Furthermore, this Constantinian connection to Britain may also have encouraged Constans to cross the Channel, although it does not explain why he would take the risk of a winter crossing – perhaps Constans merely found himself with some ‘free’ time and in the process became the last legitimate serving Roman emperor to visit Britain.

 

Well, actually, not quite... I mentioned above a caveat to the declaration of Constans’ campaign in 343 as being “the last visit to Britain by a legitimate Roman emperor”: there are in fact several things to bring up about that declaration regarding the also aforementioned usurpers and the reputed ‘end of Roman Britain’ date given, but those are for another time. For the purposes here, the caveat involves the necessity of highlighting the military nature of Constans’ visit in 343: he was possibly the last legitimate Roman emperor to campaign in Britain (and as seen, he might not even have done that).

 

This is because in 1400, some 1057 years after Constans returned to Gaul from Britain, another Roman emperor arrived on the island: Manuel II Palaiologos.

 

He is often recalled as the only ‘Byzantine emperor’ to visit Britain, but without getting into any deep discussions over the ‘Romanity’ of his title or empire, there is a continuity of imperial tradition that traces back from his Palaiologan dynasty through the successor state of the Empire of Nicaea to the main trunk of Constantinopolitan emperors from the Komnene, Macedonian, Isaurian, Heraclian, Justinianic and Theodosian dynasties to that of the Constantinians in the fourth century.

 

Rather than looking to reclaim Britain as a Roman province, Manuel II had come to England seeking aid from Henry IV against the Ottoman Turks of Sultan Bayezid I who at that very moment blockading Constantinople. He also visited the courts of Charles VI of France, Sigismund the Holy Roman Emperor, Margaret I of Denmark and Martin of Aragon.

 

  

Source Passages

 

“You [Constans] have overthrown your enemies, enlarged the Empire, and, to add greater lustre to your exploits, altering and scorning the fixed order of the seasons you have done in the winter what was never done before or will be again: you have trodden upon the swollen and raging waters of the Ocean. The wave of a sea already become almost unknown to us has trembled beneath your oars, and the Briton has quailed before the unexpected visage of the Emperor.”

Firmicus Maternus, De errore profanum religionum 28.6

 

 

137. It is not right to pass over in silence his voyage to the island of Britain, because many are ignorant about the island.138. There is a consideration that provides those who have seen it as witnesses, namely that it is a greater danger to launch a merchant ship upon that sea than to fight a naval battle elsewhere. Such fresh squalls arch the waves up to heaven, and violent winds take them up and carry them out to the boundless ocean. But the greatest danger is that, whenever the helmsman matches his skill against all the other elements, the sea suddenly sinks away beneath him, and for a time the vessel hangs in mid air above the waves and is seen to rest on uncovered sand. And if the sea sends back the current quickly, it picks up the boat once more and those on board must endure the remaining hazards. But if there is a delay in returning to the sea, the ship gradually sinks as the sand fails to support the weight upon it. 139. The emperor considered none of these risks, or rather, despite being well aware of everything, he did not hesitate. The more he knew of the much vaunted danger, the more he hastened to put to sea. And what is even more remarkable, he did not sit and wait upon the beach until when the fair weather came the ocean would calm the storm, but immediately just as things were, with the winter at its height and everything roused by the season to a peak of fury—clouds, icy chills and surf—without giving prior word to the cities there and without announcing the launch in advance, not wishing to be admired for his purpose before achieving his objective, he embarked a hundred men, so it is reported. He loosed the mooring cables and began cutting through the ocean, and all immediately changed to calm. The ocean flattened its wave and made itself smooth for the emperor’s passage, and that usual ebbing of the sea then confuted its law and held on to the land. 140. It did not happen then that while his passage to the island went so calmly, the return voyage turned out differently, but the second went better than the first in keeping with the proverb, so that there can be no dispute that this youthful undertaking was not without the blessing of God. 141. If therefore after the island had rebelled, its inhabitants were holding an uprising, and the empire was being plundered, the news had arrived, and he had been seized with rage on hearing it and had thrown the die for the voyage, to report his act of daring would not have been to the credit of his resolve, but the crisis deriving from the rebels would have taken away the greater part of the glory.

Libanius, Or. LIX

 

 

“But in Britain in the tenth consulship of Constantius and the third of Julian raids of the savage tribes of the Scots and the Picts, who had broken the peace that had been agreed upon, were laying waste the regions near the frontiers, so that fear seized the provincials, wearied as they were by a mass of past calamities. And Julian, who was passing the winter in Paris and was distracted amid many cares, was afraid to go to the aid of those across the sea, as Constans once did (as I have told).”

Ammianus Marcellinus XX.1.1

 

4. And, since in giving an account of the history of the emperor Constans I described the ebb and flow of the ocean and the situation of Britain, as well as my powers permitted, I have thought it superfluous to unfold again what has once been set forth, just as Homer's Ulysses among the Phaeacians shrinks from repeating the details of his adventures because of the excessive difficulty of the task. 5. It will, however, be in place to say, that at that time the Picts, divided into two tribes, called Dicalydones and Verturiones, as well as the Attacotti, a warlike race of men, and the Scots, were ranging widely and causing great devastation; while the Gallic regions, wherever anyone could break in by land or by sea, were harassed by the Franks and their neighbours, the Saxons, with cruel robbery, fire, and the murder of all who were taken prisoners.

Ammianus Marcellinus XXVII.8.4

 

CTh XI.16.5

Imp. Constantius [Constans] a. ad Italicum.

 

Privatas res nostras ab universis muneribus sordidis placet esse immunes neque earum conductores nec colonos ad sordida vel extraordinaria munera vel superindictiones aliquas conveniri. Et cetera.

 

Dat. VIII kal. feb. Bononiae Placido et Romulo conss. (343 ian. 25).

 

CTh XII..1.36

Idem [Impp. Constantius et Constans] aa. ad Titianum.

 

Universi omnino ex comitibus vel ex praesidibus, qui suffragio perceperint dignitates, civilibus oneribus muneribusque teneantur adstricti; plebeiam quoque sustineant capitationem, ne commoda publica cum umbratili suffragiorum pactione lacerentur. Eos tamen a praedictis oneribus excipi oportebit, qui vel in administratione vel in legationibus publicis versati sunt, ita ut, si quis contra interdictum legis nostrae precationem obtulerit, eius patrimonium fisci nostri viribus protinus vindicetur.

 

Dat. prid. kal. iul. Treviris Placido et Romulo conss. (343 iun. 30)

 


 

Bibliography

 

Crawford, P. Constantius II: Usurpers, Eunuchs and the Antichrist. Barnsley (2015)

Dodgeon, M.H. ‘The Sons of Constantine: Libanius Or. LIX,’ in Lieu, S.N.C. and Montserrat, D. From Constantine to Julian: Pagan and Byzantine Views, A Source History. London (1996) 164-205

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