How Did the Fall of Roman Britain Create King Arthur?

Discover the mythology surrounding the poorly documented period of withdrawal from Roman Britain.

May 27, 2023By Cameron Hughes, MA Field Archaeology, MA Politics

roman britain and king arthur


The collapse of Roman authority in the island province of Britannia in the 4th and 5th centuries is a historical blind spot for which the extant literary evidence is slim to none. When the western empire collapsed in the 5th century, historical literary traditions were kept alive by members of the remaining aristocracy, men such as Sidonius Apollinaris and Boethius. Meanwhile, in the east, the historical narrative was continued by historians such as Zosimus and Olympiodorus. Unlike today, a Roman historian was expected to have lived through the period he was narrating.


In post-Roman Britain, the earliest historical source we have is that of the monk, Gildas. Gildas was estimated to have written his version of events surrounding the end of Roman Britain more than a century after the fact. Added to this, his narrative was not intended to be historical but rather to provide context for the woes of his contemporaries. Other medieval writers drew heavily from Gildas’s flawed story and over centuries, and this lack of certainty has given rise to the myths and legends of British folklore.


Roman Britain and the Roman World

A sculpture of the mythical King Arthur stands watch over the cliffs of Tintagel Castle,2022, via the Cornwall Guide


The classical civilizations of the Mediterranean world had long heard rumors of a mystical wintry island far off to the north inhabited by strange peoples. In the mid-5th century BCE, Herodotus briefly described the wealth of tin in these mysterious isles. A century later, a Greek explorer, Pytheas of Massalia (modern Marseille in Southern France), a contemporary though not acquaintance of Alexander the Great, supposedly circumnavigated the entire island. Around this time, the Phoenicians established a trade route to the island, with Punic coins being found there dating to the 3rd century BCE. Britain remained a realm of curiosity to the civilized world which spurred Julius Caesar’s expeditions to the islands during his Gallic campaigns (58-50 BCE). Caesar had ventured to the island partly because it was harboring fugitives and supporting his enemies in Gaul, and partly out of a sense of adventure and for the political rewards he would accrue as a result.


Following Caesar’s political ascent, the Roman world was thrust into decades of political turmoil and transformation. This meant that Britain remained free of Roman domination for nearly another century. The reformer who emerged as the master of Rome, Augustus, bequeathed advice to his successors regarding the frontiers of the empire. Instructing them to maintain the Roman dominion within its natural boundaries; the Atlantic to the west, the Rhine and Danube rivers to the north and northeast, the Caucasus mountains and Euphrates river to the east, and the Sahara desert to the south. However, desperate for glory, Augustus’s successor sought to add Britain to their domains and in 43 CE, under Emperor Claudius, they did so.

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The Roman view of Britain as it relates to the geography of the classical world, prior to Caesar’s expeditions, by Francis Kelsey, 1918, via Dickinson College Commentaries


The Romans began their tried and tested methods of subjugation and assimilation in the new province of Britannia. However, before the end of the Julio-Claudian line, a serious revolt threatened to expel the Romans from their latest conquest. Boudica, Queen of the Iceni, led a coalition of the island’s Celtic tribes against Roman rule, razing the towns of Camulodunum, Londinium, and Verulamium and killing their Roman inhabitants. Her revolt was defeated by the general Suetonius Paulinus at the Battle of Watling Street in 61CE.


The Roman conquest of the island continued and the Roman governor, Agricola, was said to have defeated the last resistance to Roman arms in 83 CE at the battle of Mons Graupius (somewhere in the Grampian mountain range), though no definitive proof of this event has emerged. Not long after this, the Romans retreated (c.122 CE) to the line of Hadrian’s wall in northern England, relinquishing their control of what is modern Scotland. Attempts were made (c.142 CE) to re-establish this frontier further north to the region between the firths of Clyde and Forth although this too was abandoned.


For the next three centuries Britannia remained, for the most part, an obsequious province of the Roman empire, hosting three legions, largely garrisoned along the northern wall to defend against raids. This large military presence made Britain an important arena in the Roman political scene. During the year of the five emperors (193CE) one of the more serious contenders to the imperial throne, Clodius Albinus, was able to stake his claim due to the backing of his British army. The victor in that contest, Septimius Severus, eventually died in Britain on campaign and the British army hailed his sons as emperors. The British legions also helped launch the imperial careers of Constantine the Great in 306 CE and the usurper (of Honorius) Constantine III in c.407-409 CE.


The provincial division and principal cities of Roman Britain before its abandonment, via Wikimedia Commons


The province remained an integral part of the Roman world well into the twilight of the Western empire, with the Constantinian, Theodosian, and Valentinianic dynasties all campaigning to protect the island from various internal and external threats. However, as we shall see, the late 4th century saw the gradual erosion of Roman authority on the island. So much so that by the early 5th century, and likely sooner, Britannia had been irrevocably lost as a possession of the Roman emperors.


Gildas and the Literary Sources

The Venerable Bede, inspired by Gildas and inspiration for Geoffrey of Monmouth and Nennius, via Encyclopaedia Britannica


The 6th-century monk, Gildas, is the earliest British source we have for the end of Roman Britain. He was well-traveled and had likely made a pilgrimage to the eternal city itself. In a scathing critique of his contemporary British rulers, a patchwork of Anglo-Saxon and Celtic kingdoms, Gildas narrates the origins of the calamities facing his people. His writings, On the Ruin of Britain or De Excidio et Conquestu Britanniae, were the primary source material for the 8th-century monk, Bede, and together their works were the basis for the Arthurian legends of the 9th-century monk, Nennius, and the 12th-century monk, Geoffrey of Monmouth.


Map detailing the Roman retreat from Britain and the resulting barbarian raids, via Wikimedia Commons


The part of Gildas’ story that relates to the separation of Britain from the Roman empire runs as follows. Magnus Maximus raised a revolt in Britain against the Western emperor, Gratian. Maximus then left Britain with the vast majority of its army and fighting youth. The Picts (from Scotland) and Scots (from Ireland) then began raids on the undefended towns of Britain. The towns send a plea to Rome which is answered with military assistance against the raiders. The Romans constructed a frontier fortification (likely a mistaken chronology of Hadrian’s or the Antonine wall) and leave again.


The raids resume and the Romans return to assist and advise the Britons to return to the continent with them as no more help will be forthcoming. Once the Romans left for a second time the island was again overrun with Picts and Scots. Bede largely mirrors this narrative, although he places the 410 CE sack of Rome prior to both Roman expeditions to Britain, implying they took place as late as the 410’s or 420’s.


Even though Zosimus is credited with the official narrative on the end of Roman Britain, the British sources tell a different story. According to Zosimus, following the British-based revolt of Constantine III, the remaining municipal magistrates in Britain established a sort of ruling council while awaiting the resumption of imperial authority. However, following a c.410 CE plea for aid, Emperor Honorius instructed the Romano-Britons to look to their own defense. Zosimus was writing from the Eastern Roman court, nearly a century after the event, and his writings on Britain are theorized to have really been about the Bruttium region of Italy or even the Raetia region of Austria. Therefore, Gildas’ account is likely more reliable, though undoubtedly imperfect.


Vortigern and Ambrosius Aurelianus

Artist’s impression of Ambrosius Aurelianus, who supposedly led the Romano-British resistance against barbarian incursions, via


A man named Vortigern (whether this be nomenclature or titular is uncertain) emerged as a leader of the rump council governing Britain. He seems to have been one of the remaining Brittonic tribal kings, perhaps one of the Demetae, who rose to prominence in the absence of Roman power. Vortigern sought help from the Saxons against the Picts and Scots.


Bede names the mythical brothers Hengist & Horsa as leaders of this mercenary force. Bede also adds the Angles and Jutes to the tribes coming to Britain’s aid. However, it seems the Germanic force soon became enamored with the province, and betrayed Vortigern and the Romano-Britons, conquering and settling parts of the island for themselves. Vortigern’s miscalculation brings to the stage another Romano-British leader, a legendary, though likely real figure, named Ambrosius Aurelianus.


Ambrosius was probably a Romano-British patrician, likely having had both Roman and British ancestors. After Vortigern’s failures, Ambrosius seems to have been able to rally the Romano-Britons to the defense of their island. Ambrosius began a campaign against the Saxon invaders which culminated in a victory at the Battle of Badon Hill, although it is unclear whether Ambrosius actually fought there. Other than its name, the details of the Battle of Badon remain largely guesswork. The most popular estimates place the battle 44 years prior to Gildas’ writings (itself of an unknown date) during the early 6th century and somewhere in the region of modern Bath.


The baths at the Roman city of Bath, supposedly near the site of the Battle of Badon, photo by Joe Daniel Price, via Lonely Planet


The battle supposedly stemmed the Anglo-Saxon tides crashing against British shores for some generations, though not indefinitely. Coincidentally there is a marked decrease in the Anglo-Saxon archaeological footprint between c.500 and 550CE, suggesting that there was some sort of political or military reversal. Ambrosius Aurelianus also proves to be the figure who bridges the gap between history and mythology in sub-Roman Britain. In fact, he is likely the inspiration for the Arthurian legend.


King Arthur

King Arthur, by anonymous, 17th century, via British Museum


The figure of King Arthur is the only figure of this era to remain relevant in modern popular culture. The earliest mention of Arthur as a historical actor is in the Historia Brittonum, generally ascribed to the 9th-century Welsh monk, Nennius. Arthur appears in Nennius’s tale around the same time Ambrosius appears in the narratives of Bede and Gildas. While Gildas admits that under the leadership of Aurelianus, the Romano-Britons pushed back the Saxons with occasional setbacks, Nennius credits Arthur with 12 battles and 12 victories. Badon is the last of these. Nennius does mention Ambrosius as a King of the Britons, but Arthur is the hero of his focus.


It is unknown whether Aurelianus fought all the way to Badon in his campaign against the Saxons. There remains the possibility that a later war leader, unknown to Bede and Gildas, emerged to lead the Romano-British remnant. However, it is more likely that Nennius confused the two men or added some extra flare of his own.


This Arthurian figure was then used by the 12th-century Welsh cleric, Geoffrey of Monmouth, in his History of the British Kings. Geoffrey added to the legend the tales of Excalibur, Tintagel, Uther Pendragon, and Merlin while the later French poet, Chrétien de Troyes, added Lancelot and the Holy Grail. Geoffrey seems to have been constructing a mythology for Britain akin to the Greek Iliad or the Romans Aeneid as he claims the Trojan exile Brutus as the first of the British Kings, and he gifts Constantine the Great to the lineage of Arthur.


Remains of Tintagel Castle on the Cornish coast, an important part of Arthurian mythology, photo by David Levene, 2019, via


It seems that Geoffrey and the later French writers sought to romanticize the legend of Arthur as a bastion of their pious and noble, yet imperfect Medieval Christian virtues. But they also simply used him to entertain and amuse. A comparable figure from the early Middle Ages being that of Charlemagne’s Frankish Paladin, Roland. From these evolutions in folklore, we can observe how man becomes myth, and how a national origin story can be birthed from the sparsest of information.


Myth vs Fact

Statue of Constantine the Great outside York Minster, York, England, by Dan Stanek, via Learn Religions


Having traced the history, we can now summarize the mythology and the facts. Firstly, the myth, which is essentially the origin story of early England from Roman Britain, gives us Arthur as its first hero instead of the Roman Aeneas, or Greek Achilles. Pieced together, the myths tell a tale of a Britain falling into ruin after the Roman departure, being assailed on all fronts by barbarians, Picts, Scots, and Saxons.


Constans assumed the kingship of Britain but was deposed by the tyrant, Vortigern. Constans’ brothers, Uther and Ambrosius Aurelianus then fled to Brittany. When Vortigern’s Saxon mercenaries turn on him, the royal brothers return, kill him, and Aurelianus becomes king. Uther, with the help of the wizard Merlin, brings the stones for Stonehenge over from Ireland and eventually succeeds Aurelianus as king.


Title page from The Boy’s King Arthur (1922) by N. C. Wyeth, via Wikimedia Commons


Uther becomes Uther Pendragon and fathers a son, Arthur, after a magical conception in the castle of Tintagel. Arthur’s reign sees him fight twelve battles against the Saxons as they try and conquer Britain, supposedly vanquishing them finally at the Battle of Badon. With his capital at Camelot, Arthur creates a vast empire including all of Britain, Ireland, Iceland, the Orkneys, Norway, Denmark, and Gaul, defeating the fictitious Roman Emperor, Lucius Tiberius, and preparing to march on Rome itself.


Before taking the eternal city, Arthur is forced to return to Britain to defend his throne and his wife, Guinevere, against his evil nephew, Mordred. Though victorious, he is gravely wounded in battle and is taken to Avalon, where his sword Excalibur was forged, to recover from his wounds, but he is never seen again.


King Arthur (center), Charlemagne (left), Godfrey of Bouillon (right), print by Hans Burgkmair the Elder, block cut by Jost de Negker, 16th century, via British Museum


It is clear that Geoffrey of Monmouth’s writings were influenced by his own historical understandings of the Scandinavian, Frankish, and Roman worlds that had unfolded during the post-Roman period in Britain. The truth is nearly as interesting, although nowhere near as fanciful, as the myth. In reality, after a series of usurpers used the Roman army of Britain to launch their political ambitions on the continent, the island was left devoid of defense.


Coming under increasing attack from the Picts and Scots, the Britons repeatedly begged the Roman authority for aid. Some of these pleas were answered but persistently bogged down by continental engagements, including wars with the Goths and Huns, the Romans soon abandoned the island entirely.


With the absence of central taxation or administration, the magistrates of the cities of Britain seem to have formed a sort of cooperative council to plan the defense against their assailers. The influence of Vortigern may have persuaded this council to pool their wealth, and to contract the services of Saxon mercenaries. Impressed with the fertility and ease of the lands they observed these Saxons gradually began to settle the eastern lands of Kent.


A Romano-British patrician, Ambrosius Aurelianus, led a resistance effort against these Germanic settlers which may have culminated in a victory near modern Bath. For more than a generation, this stemmed the tides of migration to a trickle, but eventually, the Saxons, Angles, and Jutes returned in greater numbers. The Romano-British remnant had by now begun to abandon their urban centers and return to agricultural lifestyles. However, the return of the Germans saw these feeble farmers pushed into the Welsh mountains and Cornish hills, with a few escaping to Brittany.


Roman Britain and King Arthur

The early Germanic settlement of Britain and the retreat of the Romano-Britons westward, via Wikimedia Commons


The Romano-British diaspora in Brittany would eventually merge with the Norman race and return to Britain to conquer the Anglo-Saxon kingdom. However, their substance was slowly eroded throughout the 5th and 6th centuries, which saw the final collapse of the lifestyles and institutions that comprised Roman Britain.


The once proud provincials were pushed by the Anglo-Saxons into the hills and mountains which their ancestors had used to resist the Roman invaders centuries before. Later writers would try and use Arthurian legend as a beacon of courage and virtue to mask the ignominious truth of their real beginnings and some (fairly) still find it more pleasing to print the myth.

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By Cameron HughesMA Field Archaeology, MA PoliticsCameron is a contributing writer with an interest in the transitional period between late antiquity and the early Middle Ages in Europe. He holds an MA in Field Archaeology from the University of York, and an MA in Politics from the University of Birmingham. His Masters dissertations have been on the end of Roman Britain and the concept of ‘crisis centuries’ in Western history.