c.375-385

Birth of Aurelius Ambrosius (Ambrosius the Elder).

c.390-397

Association with "Circle of Ambrose".

c.405-415

Aurelius Ambrosius joins the Roman senate.

406/417-20

Most probable period in which Aurelius Ambrosius was appointed consular governor of Maxima Caesariensis.  Best chronological fit would be between 417-420, and necessitate a Roman attempt to regain authority in parts of the old British diocese. Similar attempts were made in Armorica and northern Gaul, at this time, with varied and intermittent success.

c.410-425

Aurelius Ambrosius is the official representative of Honorius to British provincial council.  "Wearing of the purple."  Possible failure of effective Roman support during this time.

c.418-425

Rise of influence and power of Vortigern, culminating in his High-Kingship.

425

Beginning of Vortigern's High-Kingship over much of Britain.  The provincial council has decided, external factors dictate, the need for strong, central, leadership.  Aurelius Ambrosius can offer no firm alternative.

428/9

First use of Saxon foederati by Vortigern.

429

First visit of St. Germanus to combat Pelagianism.  The doctrine is supported by Vortigern. Legendary assistance, by St. Germanus, in founding of Welsh dynasties in conjunction with Vortigern's sons.  Hallelujah Victory.

c.432-436

Decision of council, led by Aurelius Ambrosius, to relocate Cunedda and followers to parts of Wales to counter the Irish threat.  Vortigern acquiesces and assigns Ambrosius "Dinas Emrys and all the western lands".  i.e.,  Ambrosius becomes the architect for the defence of these areas. This was motivated by the councils reluctance to depend entirely on German mercenaries, with their constant demands for increased provisions, especially in an area were they would be lightly supervised.  Cunedda and his followers would be self-supporting.

c.433-438

Birth of Aurelius Ambrosius Aurelianus.  His mother was probably of British descent and considerably younger than Ambrosius the Elder.

c.435-437

Delivery of Kent to Hengist and Horsa by Vortigern.  In part for the hand of Hengist's daughter, in part to compensate for the British councils refusal to increase provisions to Vortigern's Kentish foederati.

437/438

Open rift between Ambrosius' faction and Vortigern.  Battle of Wallop.  Probably followed by a period of civil strife in eastern and southern Britain.

439-440

German foederati take advantage of British unrest and openly revolt, citing  as cause, failure of  British to supply provisions.  Flow of provisions may have been reduced to nil as a consequence of British civil war.

441

Gallic chronicles report large sections of Britain under German control following Saxon revolt.  Communications between Britain and Gaul disrupted.

442/443

Probable death of Ambrosius the Elder, "who was killed in these same broils", i.e. the Saxon revolt.  Ambrosius' surviving family is in hiding by now.

441-450

British resistance to Saxons under the leadership of Vortigern's sons, especially Vortimer and Categirn.  Four major engagements and several minor ones take place. Categirn and Horsa are killed in the fighting.

447

Second visit of St. Germanus to Britain.  By this time, Saxons are contained in some areas by Vortimer.

c.450-451

Probable death of Vortimer. British offensive stalemates.

c.455

British betrayal at peace conference. Collapse of British military in east and south of Britain.  Vortigern cedes territory to gain his freedom but, despised by all, dies shortly after.

c.455-460

British, lacking strong leadership, are overwhelmed.  Saxons raid from Kent to the Severn valley. Mass migration of British upper class to Armorica.

c.460

Aurelius Ambrosius Aurelianus becomes involved in British affairs, organising British resistance.  During a period of respite, many British flock to his standard. He initiates a British counter offensive.

460s-480s

Extended period of fighting to and fro.  Fortification of defensive sites and stationing of troops by Ambrosius.  Ambrosius is recognised as High-King by much of Britain. Assistance of the "warlike Arthur" in the latter part of his reign, who commands the mobile field force.

480s

Death of Ambrosius.  His sons rule small kingdoms in the east and south of Britain. Arthur remains active, and may have claimed the High-Kingship.

c.500

Battle of Mons Badonicus.

c.521

Battle of Camlann. Maeglwn of Gwynedd claims supremacy over British.

c.540-545

Gildas writes De Excidio Brittaniae,  Ambrosius' grandchildren are active: "His descendants in our day have become greatly inferior to their grandfather's excellence."

c.545

There is plague in Britain, the British are much more seriously afflicted than the Saxons.

547

Death of Maeglwn of Gwynedd.

c.550

Resumption of Saxon advance.