c.450 to c.550. Prehistory of Anglo-Saxon England
While it seems clear that there was a strong Anglo-Saxon presence in Britain starting in the second half of the 5th century, for the first hundred years or so it is impossible to put together a detailed and reliable account of what was going on.
Gildas, writing in the mid-6th century, provides a near-contemporary account, but few details. He notes that after the initial Saxon revolt, which rampaged unchecked over the whole island, some of the Britons surrendered, some fled overseas or into the deep forests, and some eventually got together under the leadership of the Roman commander Ambrosius Aurelianus. After this, victories went sometimes to the Saxons, sometimes to the Britons, until the battle of mons Badonicus. This was pretty much the last British victory, and Gildas seems to tell us it took place in the year of his birth, 44 years before he wrote. Elsewhere Gildas tells us that access to many of the shrines of British saints had been cut off by the "partition with the barbarians", so it seems likely that large parts of what would become England were already in Anglo-Saxon hands in his day.
This account is plausible, but it must be remembered that at least in its earlier sections Gildas's history is sometimes wildly inaccurate or deliberately changed to make his polemical points more clearly (see entry on c.450). We have no independent evidence of the existence or nationality of Ambrosius Aurelianus, though he may well be the historical model for the legendary King Arthur. Since we do not know when Gildas was born or when he wrote his De Excidio, we cannot date the battle of Mount Badon, nor can we locate it. Archaeological evidence does however show that Anglo-Saxon artefacts were found over much of England by the early 6th century, and in much greater concentrations by the mid-6th century, which corroborates Gildas's statement that several parts of Britain were inaccessible because of the barbarians. Gildas's statement that some Britons fled overseas is also supported by evidence of British settlers from Holland to Spain, though the densest area of settlement was the peninsula of Armorica, which became Brittany.
Bede, from his vantage point in the 8th century, repeats Gildas's account but otherwise adds very little between the coming of the Anglo-Saxons in the mid-5th century and the coming of the Roman missionaries to convert them at the end of the 6th. We can only imagine what Bede might have told us about the pagan past if he had wished: his focus in his Ecclesiastical History is almost exclusively on the English Church and on Christian English kingdoms.
The 9th-century Anglo-Saxon Chronicle gives more dates, mostly of the arrivals of Saxon war-parties, their fights with the British, and the succession to the new-founded Saxon kingdoms of Kent, the West Saxons, and the South Saxons. While there are details here, they cannot be accepted as reliable: since the Saxons would have been illiterate from the invasions in the 5th century until their conversion in the 7th century, the dates and details are at best a matter of traditions and later guesswork. Very close parallels between the West Saxon and Kentish stories (not only following the same framework, but allowing the same number of years between events) strongly suggest that one was copied from the model of the other, which would mean that almost half of this part of the Chronicle could be dismissed outright. Further problems with the chronology of the West Saxon entries (which suggest that a set of annals originally starting in the mid-6th century was rewritten to begin in the late 5th) and the cast of characters of the Kentish entries (many of whom seem to be semi-divine figures of myth rather than real people) will be dealt with in separate entries on the legendary foundations of these kingdoms (see c.450 to 512 and 495 to 594)..
Some other Chronicle entries, by which arriving Saxons give their names to local settlements, look suspicious for another reason. While it is possible that a chieftain called Port arrived in 501 and landed at Portsmouth which was named after him, it is more likely that the name Portsmouth derives from Latin portus, "harbour", especially since no other Englishman was ever called Port. While there were other people called Wihtgar, the Wihtgar who is said to have arrived in 514 and was eventually buried at Wihtgaraburg on the Isle of Wight is most probably a later invention or misunderstanding, since Wihtgaraburg does not in fact mean "Wihtgar's fortress" but "the fortress of the inhabitants of Wight". A more prosaic explanation probably also lies behind the name of the Netley Marshes, which are said to be called after a British king Natanleod who was killed there in 508: since "Natanleod" bears no relation to any known British personal name, the marshes are probably so named because they are wet (OE næt, "wet" + leah, "meadow"). Such invention of past heroes based on misunderstood place-names is not limited to the Chronicle: Bede claims that Rochester was named for one of its chieftains called Hrof (HE, ii.3), whereas in fact we can see that the English form of the name is derived from the earlier British form which means not "Hrof's settlement" but "the bridges of the stronghold". Not all of the characters in early Chronicle entries can be dismissed as mistaken explanations of place-names, but it is likely that Port and Natanleod and Wihtgar, at least, are figments of later fiction rather than of 6th-century fact.
This leads inevitably to the question of that much more famous shadowy 6th-century character, King Arthur, who is supposed to have led the Britons successfully against the Saxons. His existence also seems to be confirmed by chronicles: the Annales Cambriae state that he fought at Mount Badon in 516 and died with Medraut (Mordred) at Camlann in 537. Further, the 9th-century Historia Brittonum lists twelve of his battles, leading up to his victory at Mount Badon. However, it seems that at least for the 6th century the Annales Cambriae are no more contemporary than the Anglo-Saxon Chronicle, and the two Arthurian entries were probably added in the 9th or 10th centuries. The Mount Badon annal seems to be based on the Historia Brittonum, and both are undermined by the fact that Gildas in the 6th century attributes this victory to Ambrosius Aurelianus rather than to Arthur. Gildas could have been mistaken, but a closer examination of "Arthur's" twelve battles shows good reason to re-attribute another seven to other people or situations, which suggests that famous battles came to be attributed to Arthur regardless of who originally fought them. Two of the remaining four "Arthurian" battles appear from other early sources to be entirely mythical, one a fight against werewolves and one a battle in which trees are magically animated to fight. It may then be that Arthur was originally a legendary hero of folklore who fought supernatural battles, and came to be seen as the greatest of heroes (a reference to a hero who strove valiantly "but was not Arthur" in a poem about a 6th-century battle would make sense in this context), and eventually had various "historical" battles attached to him. The Irish folk-hero Fionn underwent a similar transformation, from a mythical beginning to association with the defence against the Viking invasions of Ireland. [A thorough investigation of the historicity of Arthur, with detailed bibliography up to 1997, appears at http://www.users.globalnet.co.uk/~tomgreen/arthur.htm.]
J. Campbell (ed.), The Anglo-Saxons (London: 1982), pp.23-7
O. Padel, "The Nature of Arthur", Cambrian Medieval Celtic Studies 27 (1994), pp.1-31 [more comments and bibliography up to 1997 appear on Thomas Green's web page at http://www.users.globalnet.co.uk/~tomgreen/arthur.htm]
P. Sims-Williams, "The settlement of England in Bede and the Chronicle", Anglo-Saxon England 12 (1983), pp.1-41
B. Yorke, "The Jutes of Hampshire and Wight and the origins of Wessex", The Origins of the Anglo-Saxon Kingdoms (London: 1989), pp.84-96