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Post-Roman Britain

Ambrosius Aurelianus

by Peter Kessler, 1 April 1999. Updated 16 May 2018

Ambrosius Aurelianus was, according to the later legends, high king of the Britons after Vortigern. Although the reality of his role is clouded by much uncertainty (to say the least!), his impact on this period in Britain's history seems to have been significant.

The early references

He is mentioned in four early texts, the first and oldest of which is De Excidio et Conquestu Britanniae, a sixth century diatribe against the lazy and apathetic British people and five corrupt British kings, rulers of what he referred to as 'contemptible principalities'. It was written by the British monk, Gildas, who said that Ambrosius alone was worthy of praise among his countrymen for his leadership of the British counteroffensive against the invading Anglo-Saxons.

He is credited with standing against the tide of invasion and heartening his countrymen by his own courage, and he seems to have done much to prevent the early break-up of post-Roman Britain in the face of a Germanic onslaught which must have seemed unstoppable.

It is possible that he was behind the construction of the Wansdyke as part of his efforts.

Gildas refers to him as a 'Roman', which clearly implies his continuation of Roman methods of organisation and operation. It also reflects upon his family and background, as he seems to have been brought up in a typically upper class Romanised British environment, the son of Ambrosius 'the Elder' and his young wife.

Gildas goes on to say that the Saxon advance was halted by a stunning British victory at Mons Badonicus (Mount Badon), which is believed to have been fought in the late fifth century (with the year 496 serving as a pinpoint for the purposes of information here).

This victory so stunned the German incomers that an entire generation of peace was bought for the British. This is borne out in archaeological evidence which finds a sudden cessation of Saxon advances in the south until the mid-sixth century. The Anglo-Saxon Chronicle also goes very quiet at this stage. Effectively, the outcome of the battle destroyed the ability of the Germanic participants to mount an effective retaliation (primarily, it seems, the Cantware and Suth Seaxe, and possibly also the Thames Valley Saxons).

Gildas stops short of naming the commander of the home forces at Badon, but subsequent centuries have given that credit to Arthur. This is entirely possible, as Ambrosius would have been at the height of his power in the third quarter of the fifth century and, by 496, a successor is more than likely, with Arthur fitting the bill as the then-battle leader of the Britons, and perhaps high king or emperor along Roman lines.

Romano-Britons burying treasure
With discord building in the country between about 420-450, many Romano-Britons left in a hurry, burying their wealth in the hope that they could return in better times to collect it


The second reference to Ambrosius comes from the Venerable Bede, an eighth century monk of the monastery of Jarrow, in the well-written A History of the English Church and People.

In a statement which seems to support Gildas, Bede calls him 'Ambrosius Aurelius, a modest man of Roman origin, who was the sole survivor of the catastrophe in which his noble parents had perished'.

The catastrophe refers to the Saxon foederati revolt which occurred in the early 440s, and which spread terror throughout southern Britain, persuading a large chunk of the aristocracy to emigrate to the more stable Armorican principalities. Bede tells us that 'under his leadership the Britons took up arms, challenged their conquerors to battle, and with God's help inflicted a defeat upon them'.


Nennius, a monk who lived in Bangor, was the early ninth century (supposed) compiler of an eclectic mass of material called the Historia Brittonum.

This is a fascinating document of uncertain historical reliability. It was the first serious attempt after Bede to put down the history of the Britons onto paper. Nennius seems to write about two different figures named Ambrosius, quite possibly confusing the later commander of the Britons with his father, Ambrosius 'the Elder'.

In the first case, Nennius refers to a clearly legendary Ambrosius as being a fatherless child who displayed prophetic powers before Vortigern (he could well have got his references confused here as this refers to the life of Myrvin, the later Merlin of Geoffrey of Monmouth's History of the Kings of Britain).

Nennius also says that Ambrosius was a rival whom Vortigern dreaded - but does this refer to the elder Ambrosius, as this man is described having fought Vortigern at the battle of Guolloppum (Cat Guolph, Wallop in Hampshire) around 437 or 438, when internecine warfare broke out between the two rival factions? Possibly, although the younger Ambrosius must have been pretty young if it was in fact him.

Roman Aquae Sullis (modern Bath)
Shown here is an artist's impression of the Roman city of Aquae Sulis, a stronghold during the time of Ambrosius but now buried under modern day Bath in Somerset

In a later passage, Nennius calls the younger Ambrosius 'the great king of all the kings of the British nation', essentially confirming his status as high king or emperor of Britain.

What can also be strongly inferred, both from archaeological and textual evidence, is that Ambrosius came to control the West Country area around Gloucester, enjoying direct rule of this region rather than through client kings, allies, or subjects.

Nennius has Vortigern making a gift of the land, perhaps to try and placate a potential political enemy. However, whether Ambrosius (presumably 'the Elder') gained the land (which neighboured Guenet which itself is usually thought to include Mount Snowdon and Dinas Emrys) as a gift, or whether it was gained after Vortigern's death, the younger Ambrosius apparently did use the region as a base.

If this is true, then in all likelihood he passed it onto his descendants as a single kingdom which only later divided into the Caer Baddan, Caer Ceri, and Caer Gloui which were conquered by the West Saxons in 577.

Geoffrey of Monmouth calls him Aurelius Ambrosius, and says that when King Constans was murdered by the usurper Vortigern, Ambrosius and his brother, Uther, were smuggled to Brittany (Armorica) to gain strength to return to campaign against Vortigern.

Death of Ambrosius

In time, Ambrosius defeated Vortigern, warred successfully against the Saxons and had their leader killed - Hengist of the Cantware in Kent (in AD 488 - an act which may have been incorrectly attributed to him).

According to Geoffrey, Vortigern's son, Paschent, ruler of Buellt, eventually had Ambrosius poisoned (which seems to support the idea of a date of death for Ambrosius of around 480). This also fits in with the idea of Arthur (or one of his supporters) being much more likely to be responsible for Hengist's death and the victory at Mount Badon.

Whether Ambrosius was a 'king' of the Britons, a war leader against the Saxons, a Briton, a Roman, all of the above or none of the above, isn't known for sure outside the legends and tales about him.

Some have thought that Ambrosius and Arthur are really one and the same, others that he was Arthur's uncle. The truth is probably that Ambrosius Aurelianus was a genuine, heroic, fifth century, Romano-British war leader, some of whose own exploits have been applied to the legend of Arthur.

Given the confusion by some over their respective periods of rule, this isn't surprising, but in all likelihood, Ambrosius 'the Elder' was active between about 410 and the end of the civil war against Vortigern (circa 440), while his son, Ambrosius Aurelianus, was active from some point soon after the date of Vortigern's death circa 455 to somewhere around 480.

By that time, it seems likely that Arthur led the battle from around 480-511.



Text copyright © P L Kessler. An original feature for the History Files.