By AD 550, the long peace which had lasted since Mons Badonicus was all but over. Large inroads into British territory were being made by the West Seaxe. With the Wiltsaete pushing against their south-western border, and the West Seaxe forcing their way up from the south, the British stronghold of Caer Gwinntguic collapsed in 552, opening the whole of Salisbury Plain to the Saxons.They made the most of it by sweeping round Caer Celemion, which continued to hold out, and began a takeover of the Saxons in the Thames Valley and Chilterns (from circa 571 onwards).British Cynwidion continued to hold out, although its territory was much reduced by the Middil Engle making large inroads from the Midlands.In the Midlands, the Iclingas were just beginning to absorb Angle neighbours to their immediate east and south. The large territory of Powys was divided in two from circa 570, with the eastern half becoming Pengwern.In Ebrauc, Angles staged a takeover of the region of Deira (British Deywr). Ebrauc found itself under siege from two sides, and lost ground between circa570-580.
The Roman administration of Britannia officially came to an end in AD 410, although in practise the Romano-British had governed themselves for some time.
The reorganisations of Magnus Maximus, in the 380s, which had secured Britannia's western and northern borders, had begun to break down. Northern Britain was fragmenting as it was divided piecemeal between surviving sons. Its final division seems to have come in circa 470 with Ebrauc losing its western arm, the Pennines.
Likewise, Powys was divided in two following the civil war between Vortigern and Ambrosius Aurelianus. Middle Britain, in the more highly civilised heartland of sub-Roman Britain, was apparently also in the process of a slower break-up.
Along the Saxon Shore, former laetisettlements and waves of new arrivals were asserting their independence. Hengist and Horsa led the swift conquest of eastern Ceint, while Saxon groups pushed deep into the Thames Valley, and Angles invaded Caer Went and Linnius. Only Bernaccia and Deywr seemed to have peaceful Angles on their coastlines.
Twenty five years after the start of the Anglo-Saxon Conquest, the North remained untouched and still relatively powerful. Angles hired as mercenaries(laeti) continued to help defend the eastern coastline.
The Lindisware (Linnius) Angles appear to have managed a peaceful transition of power. They took on many aspects of sub-Roman administration and lived isolated from the action in the south.
Although the country was in a state of flux, this was the time of Ambrosius Aurelianus, and Arthur too. Together, or in sequence, they organised the much-needed defence of the south: groups of Angles were rapidly colonising Caer Went and penetrating Caer Lerion; the Cantware Jutes conquered Kent by 488; Ælle's Saxons made swift progress on the south coast; and more Saxons had made deep inroads along the Thames Valley, carving out settlements there and threatening the entire West Country. Cynwidion quickly lost its western border to the Ciltern Saetan, while the territory of Lundein was swiftly occupied by the Middel Seaxe on either side of the Thames. Defence came in the form of the battle, or siege, of Mons Badonicus incirca 496.
More than any other battle or siege, Mons Badonicus had a massive effect on the conquest. Probably led by Ælle, who was the recognised overlord of the invaders, the Saxons of the south had suffered a crushing defeat which seems to have critically weakened the Suth Seaxe, Middel Seaxe, Thames Valley Saxons, and perhaps even the Cantware.
A period of peace which lasted for over a generation followed the British victory. However, Cerdic and his supporters made a grab for power over the West Seaxe in 495-519. In addition, the Angles in the east continued to pour into the Midlands, quickly engulfing Caer Lerion and apparently forcing a passage through Cynwidion's western territory to link up with the Ciltern Saetan, probably shortly before Mons Badonicus. Caer Mincip, a small British enclave, survived on the edge of the (probably weakened) Middel Seaxe kingdom.
By the end of this period the peace was fading, and the first move seems to have been made by the Bernician Angles (British Bernaccia) in 547, situated North of the Humber. Nearby Rheged and The Pennines further sub-divided, while in the south Caer Colun came under attack.
Here you will see, the gradual conquest of what will become England, in a step by step description via Map.
At the same time as the East Engle were being united under a single king, Angle and Saxon conquests during this period were rapid and extensive.
The West Seaxe defeated three British kings in 577, destroying Caer Baddan, Caer Ceri and Caer Gloui. The Hwicce moved into the territory to form their own kingdom while the West Seaxe continued to fight against Dumnonia.
That catastrophic British defeat meant that both Dumnonia and Caer Celemion were now totally isolated, while the nearby East Seaxe consolidated their own kingdom.
North of the Humber, the two Angle kingdoms were also making rapid advances. Ebrauc's defence finally ran out of steam in circa
580, by which time it was overrun by the Deiran Angles. The Bernician Angles conquered Dunoting in 595, and appear to have destroyed The Peak at around the same time. Saxon groups moved in from the Midlands to adopt the name, becoming the Pecset.
Elmet was now surrounded by enemies but North Rheged was at the height of its strength, even controlling nearby Galwyddel, until in-fighting brought down its powerful leader.
After that catastrophe, both North and South Rheged fell quickly. Only a small North Rhegedian enclave may have survived, against Caer-Guendoleu's border and probably around Carlisle. That pocket kingdom itself was absorbed by Alt Clut, while control of Galwyddel returned to the Britons on Ynys Manau.
This was a period of Anglo-Saxon consolidation. The Bernician and Deiran Angles secured the west coast, and destroyed Elmet and the Gododdin.
The Iclingas were swiftly taking over all the Middil Engle settlements in the Midlands. They became known as the Mercians - March, or border kingdom - between 584-600. By circa 630 they were masters of the East Midlands.
The East Seaxe were gaining overlordship of the Middel Seaxe and the region of theirs which lay south of the Thames, Suther-ge.
The Pecset were settling the Peak District, and the Hwicce seem to have been merging with the Britons within their new territory. The West Seaxe finally destroyed Caer Celemion, as well as expanding a little further westwards.