Ambrosius Aurelianus appears in later pseudo-chronicle tradition beginning with
Geoffrey of Monmouth's
Historia Regum Britanniae with the slightly garbled name
Aurelius Ambrosius, now presented as son of a King Constantine. King Constantine's eldest son Constans is murdered at Vortigern's instigation, and the two remaining sons (Ambrosius and Uther, still very young) are quickly hustled into exile in
Brittany. (This does not fit with Gildas' account, in which Ambrosius' family perished in the turmoil of the Saxon uprisings.) Later, the two brothers return from exile with a large army when Vortigern's power has faded. They destroy Vortigern and become friends with
Merlin. They go on to defeat the Saxon leader
Hengist in two battles at Maisbeli (probably Ballifield, near
Sheffield) and
Cunengeburg. Hengist is executed and Ambrosius becomes king of Britain. However, he is poisoned by his enemies, and Uther succeeds him. The text identifies the poisoner as Eopa. Ambrosius and Uther are supposedly raised by their adoptive maternal grandfather Guthelinus/Vitalinus. It is not explicitly covered in Geoffrey's narrative, but this genealogy makes Constantine and his children descendants of
Conan Meriadoc, legendary founder of the line of Kings of Brittany. Conan is also featured in the
Historia Regum Britanniae, where he is appointed king by Roman emperor
Magnus Maximus (reigned 383–388). Constantine's reign is placed by Geoffrey as following the
Groans of the Britons mentioned by Gildas. Constantine is reported killed by a
Pict and his reign is followed by a brief succession crisis. Candidates for the throne included all three sons of Constantine, but there were problems for their eventual rise to the throne. Constans was a
monk, and Ambrosius and Uther were
underage and still in their
cradle. The crisis is resolved when
Vortigern places Constans on the throne, and then serves as his chief
adviser and
power behind the throne. When Constans is killed by the Picts serving as bodyguards of Vortigern, Vortigern feigns anguish and has the killers executed. Ambrosius is still underage and Vortigern rises to the throne. The chronology offered by Geoffrey for the early life of Ambrosius contradicts Gildas and Nennius, and is also internally inconsistent. The
Groans of the Britons involves an appeal by the Britons to Roman consul "Agitius". This person has been identified with
Flavius Aetius (d. 454),
magister militum ("master of soldiers") of the
Western Roman Empire and consul of the year 446. The Groans are generally dated to the 440s and 450s, preceding the death of Aetius. If Geoffrey's Constantine rose to the throne immediately following the Groans, this would place his reign in this period. Geoffrey gives a 10-year reign for Constantine and his marriage lasts just as long. However the eldest son Constans is clearly older than 10 years by the time his father dies. He is already an adult candidate of the throne and has had time to follow a monastic career. Even assuming there is a time gap between the death of Constantine and the adulthood of Constans, his younger brothers have not aged at all in the narrative. Geoffrey's narrative has an underage Ambrosius, if not a literal
infant, in the 460s. Accounts deriving from Gildas and Nennius place Ambrosius in the prime of his life in the same decade. Most telling is that Geoffrey has Vortigern rising to the throne in the 460s. Nennius places the rise of Vortigern in the year 425, and Vortigern is entirely absent in chronologies of the 460s. Suggesting that he was deceased by that time. Geoffrey's narrative includes as a major character
Hengist, as leader of the Saxons. He is featured as the father of Queen
Rowena and father-in-law of Vortigern. Other Saxon characters in the narrative tend to receive less attention by the writer, but their names tend to correspond to Anglo-Saxons known from other sources. Henginst's supposed son Octa is apparently
Octa of Kent, a 6th-century ruler variously connected to Hengist as a son or descendant. The other son, Ebissa, is more difficult to identify. He might correspond to kinsmen of Hengist variously identified as "Ossa", "
Oisc", and "Aesc". A minor Saxon character called "Cherdic" is probably
Cerdic of Wessex, though elsewhere Geoffrey calls the same king "Cheldric". He actually may appear under three different names in the narrative, since Geoffrey elsewhere calls the interpreter of Hengist "Ceretic", a variant of the same name. Geoffrey, in the last chapters featuring Vortigern, has the king served by
magicians. This detail derives from Nennius, though Nennius was talking about Vortigern's "wise men". They may not have been magic users but advisers. Vortigern's encounter with Emrys/Merlin takes place in this part of the narrative. Merlin warns Vortigern that Ambrosius and Uther have already sailed for Britain and are soon to arrive, apparently to claim his throne. Ambrosius soon arrives at the head of the army and is crowned king. He besieges Vortigern at the castle of "Genoreu", which is identified with Nennius'
Cair Guorthigirn ("
Fort Vortigern") and the
hillfort at
Little Doward. Ambrosius burns the castle down and Vortigern dies with it. Having killed Vortigern, Ambrosius next turns his attention to Hengist. Despite the fact that no earlier military actions of Ambrosius are recorded, the Saxons have already heard of his bravery and battle prowess. They immediately retreat beyond the
Humber. Hengist soon amasses a massive army to face Ambrosius. His army counts 200,000 men and Ambrosius' only 10,000 men. He marches south and the first battle between the two armies takes place in Maisbeli, where Ambrosius emerges the victor. It is unclear what location Geoffrey had in mind. Maisbeli translates to "the field of Beli", and could be related to the
Beli Mawr of Welsh legend and/or the
Celtic god Belenus. Alternatively it could be a field where the
Beltane festival was celebrated. Geoffrey could derive the name from a similar-sounding toponym. For example,
Meicen of the
Hen Ogledd ("Old North"), traditionally identified with
Hatfield. Following his defeat, Hengist retreats towards Cunungeburg. Geoffrey probably had in mind
Conisbrough, not far from Hatfield. Ambrosius leads his army against the new position of the Saxons. The second battle is more evenly fought, and Hengist has a chance to achieve victory. However, Ambrosius receives reinforcements from Brittany and the tide of the battle turns in favour of the Britons. Hengist himself is captured by his old enemy
Eldol, Consul of Gloucester and decapitated. Soon after the battle, the surviving Saxon leaders Octa and Eosa submit themselves to Ambrosius' rule. He pardons them and grants them an area near
Scotland. The area is not named, but Geoffrey could be basing this on
Bernicia, a real Anglo-Saxon kingdom covering areas in the modern borders of Scotland and England. Geoffrey closely connects the deaths of Vortigern and Hengist, which are elsewhere poorly recorded. Vortigern historically died in the 450s, and various dates for the death of Hengist have been proposed, between the 450s and the 480s.
Octa of Kent, the supposed son and heir of Hengist, was still alive in the 6th century and seems to belong to a later historical era than his father. The ruling family of the
Kingdom of Kent were called the Oiscingas, a term identifying them as descendants of
Oisc of Kent, not of Hengist. In effect, none of them was likely a literal son of Hengist and their relation to Hengist may have been a later invention. Geoffrey did not invent the connection, but his sources here were likely legendary in nature. Following his victories and the end of the wars, Ambrosius organises the burial of killed nobles at Kaercaradduc. Geoffrey identifies this otherwise unknown location with Caer-Caradog (
Salisbury). Ambrosius wants a permanent memorial for the slain and assigns the task to Merlin. The result is the so-called Giants' Ring. Its location in the vicinity of Salisbury has led to its identification with
Stonehenge, though Geoffrey never uses that term. Stonehenge is closer to
Amesbury than Salisbury. The ring formation of the monument could equally apply to
Avebury, the largest stone circle in Europe. ==In other texts==