Ambrosius Aurelianus, the second son of the Emperor Constantine, was known to the Welsh as Emrys Wledig (the Imperator) or Emrys Benaur (the Golden-Headed). Geoffrey of Monmouth tells us how he was still a young child when his teenage brother, Constans' short-lived reign came to an abrupt end. With his father executed and his brother murdered, little Ambrosius, along with his brother, Uther, was bundled up and taken across the Channel to the safety of the court of his cousin, Budic I of Brittany. Here he grew up, while the evil Vortigernreigned in Britain, but always Ambrosius planned to return and claim his rightful inheritance.
His chance arrived some years later. Ambrosius returned to Britain, landed at Totnes (Devon) and it may be at this point in history that he clashed with Vitalinus (probably Vortigern or a supporter) at the Battle of Guoloph (Nether Wallop in Hampshire) as recorded by Nennius. This may have resulted in Victory for Ambrosius who was, at some point in history, "given all the kingdoms of the western side of Britain" by Vortigern. Ambrosius was, however, unsatisfied with such a compromise and the struggle between the two continued for most of his life. Vortigern's pro-Saxon policies eventually led to his downfall though and, (probably) in the late 450s, the British people finally rallied behind Ambrosius. Vortigern was hounded into taking refuge in his mountain strongholds. While under siege at Caer-Guorthigirn (Little Doward, Herefordshire), the fortress was miraculously struck by lightning. Vortigern and his entire garrison were burnt to death.
After Vortigern's death, Ambrosius was conciliatory towards his sons and let them keep their lands in Buellt, Gwerthrynion, Gwent and Powys. Despite this magnanimity, King Pasgen of Buellt & Gwerthrynion later rebelled against Ambrosius and twice attempted to overrun Britain with help from the Saxons and the Irish. The main Anglo-Saxon forces had retired North of the Humber and Ambrosius met Hengist in Battle at Maesbeli and then Conisburgh (Caer-Conan). Later he besieged Octa and Osla at York (Caer-Ebrauc). All were defeated, but Ambroius let them settle their people in Bryneich (Bernicia).
Ambrosius is credited, by Geoffrey, with the building of a monumental stone circle, the "Giant's Ring" (possibly Stonehenge or Avebury) on Mount Ambrius as a memorial to those massacred by the Saxons at the "Night of the Long Knifes" during King Vortigern's reign. He was buried there himself after being poisoned by a Saxon at Winchester (Caer-Guinntguic).
Ambrosius was certainly an historical figure as recorded by his near contemporary commentator, St. Gildas. In his "Ruin of Britain," the monk describes how the Saxons rampaged through the country before they "returned home". Then:
"The remnants (of the British)...take up arms, and challenge their victors to battle under Ambrosius Aurelianus. He was a man of unassuming character, who, alone of the Roman race, chanced to survive the storm in which his parents, people undoubtedly clad in the purple, had been killed. Their offspring in our days have greatly degenerated from their ancestral nobleness. From that time the citizens were sometimes victorious, sometimes the enemy...up to the year of the Siege of Mons Badonicus."
Added to this are the comments of the 9th century chronicler, Nennius, who, in-line with Geoffrey, recorded Ambrosius as one of the chief dreads of King Vortigern. Nennius also describes Ambrosius as a young boy without a father, called to help Vortigern out during the building of his fortress at Dinas Emrys (see Vortigern), a role later taken on by Merlin. He ties the period down by implying that Vortigern's reign had begun by at least 425, and that Ambrosius fought at Guoloph twelve years later. This is most interesting for it poses a bit of a problem. Many people take Gildas' reference to Mons Badonicus to imply that it was Ambrosius, rather than the usually attributed King Arthur, who was the commander at the famous battle of Mount Badon, the decisive British victory over the Saxons around 495-500. In the year 495, Ambrosius would have been at least 74 years old, and it would, indeed, be difficult to imagine a man of this period living to such an age, let alone wielding a heavy sword and leading a mounted charge against the Saxon positions. So what is the solution?
There isn't a definitive one, but some have solved the problem by postulating two men named Ambrosius; the elder, whom Vortigern dreaded, and the younger, the hero of the British resistance of the mid-to-late fifth century and the victor of Mount Badon. This is certainly possible. . .as there seem to have been a number of people with the same name in those days (ie. Maximus, Constantine, etc.). Why not two Ambrosii?
The more likely possibility, though, is that there was just one Ambrosius. Arthur may indeed have been the real commander of the victory at Mount Badon; or perhaps as "the great king among all the kings of the British nation," Ambrosius Aurelianus could have been the aging overall supreme commander of the engagement, with the function of front line battle leader going to a younger man, perhaps Arthur.
Geoffrey Ashe (1980) A Guidebook to Arthurian Britain.
Gildas Badonicus (c.540) The Ruin of Britain.
Peter C. Bartrum (1993) A Welsh Classical Dictionary. E.K. Chambers (1964) Arthur of Britain. Ronan Coghlan (1991) The Encyclopaedia of Arthurian Legends.
Jack Lindsay (1958) Arthur and his Times.
Geoffrey of Monmouth (1136) The History of the Kings of Britain.
John Morris (1973) The Age of Arthur.
Nennius (c.829) The History of the Britons.
John Rhys (1901) Celtic Folklore.
Hugh Williams (1901) Gildas.