The Brittonic Period–the fifth and early sixth centuries of Britain–was a pivotal period in British history and as such it remains the subject of much contentious debate. There is still no academic agreement as to the chronology or even the precise sequence of events for the Brittonic era.
Nevertheless, in recent decades a certain degree of consensus has slowly emerged among scholars that the cessation of direct Roman political control over the British Isles did not automatically spell the collapse of civilized life in the former diocese of Britannia; some manner of organized Romano-British polity continued on after the cessation of Imperial control. While virtually all texts bearing on the period remain problematical and intensely debated, the archaeology of the era has begun to tilt more in the favor of continuity than discontinuity in fifth century Britain.
Many scholars have begun to question the whole ideology of the “Anglo-Saxon Invasion.” instead arguing for a more complex process of military recruitment, trade and immigration, which only in later stages devolved into outright conflict. A few academics have even tried to make the case that southeastern Britain had already been German-speaking well before the arrival of the Romans, although this hypothesis remains an outlier. Whatever model one may choose to reconstruct the events of fifth and early sixth century Britain, however, one important aspect of the era remains virtually ignored: Brittonic sea power and its relationship to the military and political events of the era. Despite the voluminous secondary literature relating to the Brittonic Period–the storied Age of Arthur–almost no one has discussed naval aspects of Post-Roman Britain. If discussed at all, it has generally been within the context of an assumed Saxon naval dominance of Britain and its surrounding seas during the whole of the fifth and sixth centuries.
While no one questions the military importance of Saxon, Irish and Pictish sea power during this period, when it comes to the native British and their seafaring capabilities, a curious myopia affects English historiography.
It could be argued that, like the question of Arthur’s historical existence, there is no direct evidence for British seafaring for this period, much less of a Brittonic navy or fleet. To a certain extent this is a specious argument, for actual written documents relating to Britain contemporaneous to the fifth century are nearly non-existent. The written evidence that does survive consist of: inscribed stones, mostly grave markers; a copy of the Aeneid believed to have originated from a British scriptorium of the period; plus later copies of material ascribed to St. Patrick’s authorship. There are odds and ends of material from continental sources dating to the fifth and sixth centuries relating to events in Britain, but after the defeat of the British usurper Constantine III, Latin and Greek writers of the Roman Empire were little concerned with events in the former Roman diocese. Almost all other information we possess exist either as transcriptions of the oral tradition or much copied (and thus corrupted) texts dating to the periods following it. These later texts are subject to their own set of problems of accuracy or credibility. Yet the situation for Scotti, Picti and Saxons sources is the same or worse for this period: all these cultures were pre- or proto-literate and one must rely on transcribed oral traditions or later texts for evidence relating to their history as well. Yet in all these cases, no one questions their seafaring prowess or the naval influence they wielded during this era.
Despite this, we do have some evidence for the existence of Brittonic naval capabilities, albeit much of it indirect. During the late fourth and early fifth centuries, Britain acquired an odious reputation for being “fertile in tyrants.” These Late Roman usurpers of necessity had to make use of sea power to transport their armies unopposed onto the European continent. Control of the sea was thus a sine qua non for any British usurper attempting to seize the Imperial throne. The last such “tyrant” was Constantine III, who began his bid for power beginning in 405. Constantine nearly succeeded in his attempt, but he finally came to an ill end and by 514 the last vestiges of his attempt were erased.
While details of the makeup of the usurper fleets is unknown, we do know that the rank and file of the sailors would have consisted of indigenous seafarers, even if the officers commanding them might have been ethnic Romans. From later British tradition, we know that these Roman usurpers were often viewed as British by the native population of Britannia. After Constantine III’s fall, continental sources fall silent about Britain. There is no evidence that the diocese of Britannia was ever re-occupied, while there is a great deal of circumstantial evidence to indicate that, after Constantine, the Western Empire had but nominal control of most of Gaul and Hispania and, therefore, for the rest of the century a military conquest and reoccupation of Britannia was simply beyond the capabilities of the Empire. Whatever transpired in Britannia after Constantine would have happened under a native polity independent from Ravenna.
On the positive side, we do have direct evidence for the existence of British naval capabilities for the post Roman period. The late Roman writer Publius Flavius Vegetius Renatus included a section on naval affairs in his treatise on the Roman military. The naval section of his treatise De Re Militari has rarely been translated, which may account for so few scholars being aware of his mention of British naval forces. The passage is tantalizingly short, but it seems to reflect contemporary Brittonic affairs–not looking back to a previous era, as so much of Vegetius’ treatise does. While scholars debate the precise date of the tome, the best estimates places it in the reign of Valentinian III; a date between 435 and 450 would therefore not be unreasonable.
Despite the paucity of contemporary evidence, there are a few Classical sources which bear indirectly on the subject and to late Roman naval affairs in general. There also exists a large body of traditional accounts which relate to Brittonic Period seafaring and naval activities as well. As with all traditional and folkloric material, these sources must be treated with caution; nevertheless, given the conservative nature of such folk traditions, much legitimate information may be gleaned from them. Lastly, there is a growing body of archaeological and anthropological evidence which bears on the subject and which needs to be properly analyzed and interpreted freed from an anti-Brittonic bias which besets much of English historiography.
Although Saxon naval abilities and capabilities are important for the history of the Brittonic Period, they constitute only a part of the overall subject. Rather than view north German sea-power as a discreet topic isolated from the discussion of Brittonic maritime affairs, a better approach would be to see them as but an element in the larger context of general Brittonic (or British) maritime affairs.
Even after the Saxon revolt, the best archaeological evidence indicates that the native British polity remained intact and up until the mid sixth century, was still the dominant ethnic and military factor in the region. Consequentially, its naval capabilities would have also remained largely intact and substantial. In putting the admittedly fragmentary evidence together for this era, rather than assuming the indigenous folk of Britain as inherently weak and incapable of self-defense, they should be viewed as active players in the history of their island and, despite the many challenges they faced, as generally successful in their response to these challenges, at least until at least the mid-sixth century.
Throughout history the native folk of Britain and adjacent isles were renowned as seafarers. Unless there is actual evidence to the contrary, one should also posit them as skilled at naval warfare, eminently capable of both offense and defense at sea and they were certainly no less capable during this initial era of British independence as they were in later, better documented, periods.
In support of this thesis, we may look to one major aspect of Brittonic sea-power that has been overlooked or ignored by historians. This is the fact of British expansion overseas during this period. It is well known that the Celtic British of Post Roman Britain established colonies in northern Hispania and northwestern Gaul during this era. Moreover, one British ruler participated in at least one major military intervention into Roman Gaul during the fifth century. Such colonial expansion and military intervention required maritime capabilities and naval power of some considerable strength to carry out. Even if details of these fifth and sixth century continental activities remain poorly documented, the mere fact of their existence constitutes proof of Brittonic naval sea-power for the period in question.
While much new research is needed and a reassessment of old archaeological and written evidence is called for, even given the current state of knowledge, the role of sea-power in the history of Post-Roman Britain–and Brittonic sea-power–should be regarded as a basic fact, not theory.
The task for the future, therefore, is to create a synthesis of the diverse material relating to the fact of British sea-power in the fifth and sixth centuries and present it to the relevant readership.
Such a narrative may be disputed in its details, or its conclusions criticized, but ultimately it is preferable to make the attempt rather than continuing to allow so large a lacuna continue to exist in the study of the Brittonic era.
 The term Brittonic was first used by Chris Snyder to describe the distinct period following the Roman era but before Saxon ascendancy, when the native Britons and their culture flourished. This phrase is used in preference to the pejorative “sub” Roman label, or to use the now contentious phrase “Age of Arthur,” which has been much disputed and made anathema to the Minimalist school of English historiography by Professor Dumville since the 1970’s.
 See Kenneth Dark, “Centuries of Roman survival in the West” British Archaeology, Issue no 32, March 1998, and Dark, Civitas to Kingdom: British Political Continuity, 300-800 (Studies in the Early History of Britain) (Leicester: Leicester University Press, 1994); Martin Henig, “Roman Britons after 410″ British Archaeology, Issue 68, December 2002.
 Christopher Snyder “Sub-Roman Britain an Introduction” Vortigern Studies (1997)
 See, for example, Howard Williams, “Forgetting the Britons in Victorian Anglo-Saxon archaeology” in N. J. Higham, Ed., Woodbridge Britons in Anglo-Saxon England (Woodbridge : Boydell Press, 2007) ; Also see Francis Pryor, “The Invasion That Never Was,” Episode 3, Britain AD: (BBC Channel 4, 2004); print edition: Francis Pryor, Britain AD, (NY: Harper Perennial; 2005).
 Stephen Oppenheimer, The Origins of the British: A Genetic Detective Story, (London: Constable, 2006)
 The number of studies which consider Dark Age Celtic naval developments can be counted on one hand (assuming that hand has been subjected to multiple amputations). See, for example, Bernard S Bachrach, “The Questions of King Arthur’s Existence and of Romano- British Naval Operations” The Haskins Journal 2, 13-28. Although concerned with Germanic naval developments, John Haywood, Dark Age Naval Power: Reassessment of Frankish and Anglo-Saxon Seafaring Activity (London: Routledge, 1991) is also relevant. Geoffrey Ashe, Land to the West (NY: Viking, 1962) while mainly concerned with St. Brendan, disambiguated all the early Classical and Celtic references to seafaring in the western seas, and therefore is of value too. Count Tolstoy, a brilliant non-academic historian, in a wide ranging essay trying to establish a valid chronology for the period, based on the unreliable homily by Gildas, also mentions in passing Arthurian sea-power: see Nikolai Tolstoy, “Early British History and Chronology” Transactions of the Honorable Society of Cymmrodorians, 1964, pg. 308. There is, admittedly, a voluminous literature on Saxon seafaring and ships, which discuss a number of issues related to the Brittonic Navy, but which are outside the purview of this present short essay.
 Robert Vermaat, “The Vergilius Romanus: the first British book? Vergil MS Vat. lat. 3867= Romanus” Vortigern Studies; David H. Wright, The Roman Vergil and the Origins of Medieval Book Design. (Toronto, Univ. of Toronto Press 2001); St. Patrick, “A Letter to the Soldiers of Coroticus” AncientTexts.org; Mark Redknap, John M. Lewis and Nancy Edwards Eds., A Corpus of Early Medieval Inscribed Stones and Stone Sculptures in Wales (Cardiff: Univ. of Wales Press, 2007-2013) (three volumes).
 Michael Kulikowsky, “Barbarians in Gaul, Usurpers in Britain” Britannia, vol. 31 (2000), 325-345.
 See, for example, “The Dream of Maxen Wledig,” The Mabinogion, (Gwyn Jones and Thomas Jones, Eds.) (NY: Everyman’s, 1949).
 Eric Morse, “Decade of Darkness; the Collapse of the Roman Army in the West” (AD 395-405) Royal Canadian Military Institute Lecture (Toronto, Dec. 23, 2014).
 Paul D. Emanuele, Vegetius and the Roman Navy, MA Thesis, (Vancouver: Univ. of British Columbia, 1974), 28; Nikolas Boris Rankov, in 2002, in the Proceedings of the XVIIIth International Congress of Roman Frontier Studies, attempted to dismiss the notion of British naval vessels, but Emanuele had already foreseen these arguments in 1974 and successfully countered them in his thesis.
 For Britonia, see: Simon Young, “Britonia, The Forgotten Colony” History Today, Vol. 50 Issue 10 (Oct. 2000); Antonio Garcia y Garcia, Historia de Bretona (Lugo: Edita Servivio /Publicacions Deputacion Provincial, 1999). For Brittany, see: Joseph Loth, Emigration Bretonne en Armorique du Ve au VIIe siecle de notre ere (Paris: Picard, 1883); Leon Fleuriot, Les origines de la Bretagne, (Payot, 1980); John Morris The Age of Arthur, Chapter 14, 249-260. On Riothamus and his campaigns in Gaul, see Geoffrey Ashe The Discovery of King Arthur, (London: Guild, 1985), 53-56; Morris, Age of Arthur, ibid; Dane Pestano, “Riothamus and the Visigoths” Dark Age History blog, August 21 2011.
 See Christopher K. Coleman, Britain’s Best Bulwark; Celtic British Naval Power in the Brittonic Era (forthcoming).