Magnus Maximus[1] (Classical Latin: [ˈmaŋnʊs ˈmaksɪmʊs]; Welsh: Macsen Wledig [ˈmaksɛn ˈwlɛdɪɡ]; died 28 August 388) was Roman emperor in the West from 383 to 388.

[6] Maximus would become a distinguished general in the following years; as he would gain the support of his fellow soldiers and the admiration of the Romano-Britons whom he defended, which would lead to his eventual immortalisation in Welsh legend in the centuries following.

[3] The Western emperor Gratian had received a number of Alans into his bodyguard, and was accused of showing favouritism towards these Iranian speaking foreigners at the expense of Roman citizens.

Negotiations followed in 384, including the intervention of Ambrose, Bishop of Milan, leading to an accord with Valentinian II and Theodosius I in which Maximus was recognized as Augustus in the West.

[15] The Gallic Chronicle of 452 describes the Priscillianists as "Manichaeans", a different Gnostic heresy already condemned in Roman law under Diocletian, and states that Magnus Maximus had them "caught and exterminated with the greatest zeal".

"[17] Conversely, Maximus's edict of 387/388, which censured Christians at Rome for burning down a Jewish synagogue, was condemned by bishop Ambrose, who said people exclaimed, "the emperor has become a Jew".

We also encounter an otherwise unrecorded daughter of Magnus Maximus, Sevira, on the Pillar of Eliseg (9th century), an early medieval inscribed stone in Wales, which claims that she married Vortigern, king of the Britons.

[26] In the De Excidio et Conquestu Britanniae written c. 540, Gildas says that Maximus "deprived" Britain not only of its Roman troops, but also of its "armed bands...governors and of the flower of her youth", never to return.

[30] After he became emperor of the West, Maximus returned to Britain to campaign against the Picts and Scots (i.e., Irish), probably in support of Rome's long-standing allies the Damnonii, Votadini, and Novantae (all located in modern Scotland).

While there he likely made similar arrangements for a formal transfer of authority to local chiefs—the later rulers of Galloway, home to the Novantae, claimed Maximus as the founder of their line, the same as did the Welsh kings.

[26] The ninth century Historia Brittonum gives another account of Maximus and assigns him an important role: The seventh emperor was Maximianus, He withdrew from Britain with all its military force, slew Gratianus the king of the Romans, and obtained the sovereignty of all Europe.

Unwilling to send back his warlike companions to their wives, families, and possessions in Britain, he conferred upon them numerous districts from the lake on the summit of Mons Iovis, to the city called Cant Guic, and to the western Tumulus, that is Cruc Occident.

In consequence of their absence, Britain being overcome by foreign nations, the lawful heirs were cast out, till God interposed with his assistance.Modern historians believe that this idea of mass British troop settlement in Brittany by Maximus may very well reflect some reality, as it accords with archaeological and other historical evidence and later Breton traditions.

Armorica declared independence from the Roman Empire in 407, but contributed archers for Aetius's defence against Attila the Hun, and Riothamus, who may have ruled there as king, was subsequently mentioned in contemporary documents as an ally of Rome's against the Goths.

Despite its continued usage of two distinct languages, Breton and Gallo, and extensive invasions and conquests by Franks and Vikings, Armorica retained considerable cultural cohesion into the 13th century.

Legendary versions of Maximus's career in which he marries the Welsh princess Elen may have circulated in popular tradition in Welsh-speaking areas from an early date.

[31] Upon reaching the kingdom of Armorica (historically, the region between the Loire and Seine rivers, later comprising Brittany, Normandy, Anjou, Maine and Touraine), he defeated the king and killed thousands of inhabitants.

Following the death of Caradocus, rule of Britain as regent passed to Dionotus, who – facing a foreign invasion – appealed to Maximus, who finally sent a man named Gracianus Municeps with two legions to stop the attack.

While a broadly positive account of Maximian, the History concludes with the success of the barbarian invaders, and laments, "Alas for the absence of so many warlike soldiers through the madness of Maximianus!".

With the help of men from Britain led by Elen's brother Conanus (Welsh: Cynan Meriadoc, Breton: Conan Meriadeg), Macsen marches across Gaul and Italy and recaptures Rome.

According to another legend, Maximus appointed Coel Hen, perhaps the legendary "Old King Cole", as governor of northern Britain, ruling from Eburacum (York).

According to the Flores Historiarum, during the construction of the Castle and the nearby planned town, the body believed to be of Magnus Maximus was discovered entombed; King Edward ordered its reburial in a local church.