its Norman and late Medieval fortifications. The earlier British and Romano-British settlement at Segontium was named for the nearby Afon Seiont. After the end of Roman rule in Britain around 410, the settlement continued to be known as ("Fort Seiont") and as ("Fort Constantius or Constantine"), of the History of the Britons, cited by James Ussher in Newman's life of Germanus of Auxerre, both of whose names appear among the 28 civitates of sub-Roman Britain in the Historia Brittonum traditionally ascribed to Nennius. The work states that the inscribed tomb of "Constantius the Emperor" (presumably Constantius Chlorus, father of Constantine the Great) was still present in the 9th century. (Constantius actually died at York; Ford credited the monument to a different Constantine, the supposed son of Saint Elen and Magnus Maximus, who was said to have ruled northern Wales before being removed by the Irish.) The medieval romance about Maximus and Elen, Macsen's Dream, calls her home ("Fort Seiontmouth" or "the caer at the mouth of the Seiont") and other pre-conquest poets such as Hywel ab Owain Gwynedd also used the name . The Norman motte was erected apart from the existing settlement and came to be known as , "the fortress in Arfon". (The region of Arfon itself derived its name from its position opposite Anglesey, known as in Welsh.) A 1221 charter by Llywelyn the Great to the canons of Penmon priory on Anglesey mentions ; the Brut mentions both and . In 1283, King Edward I completed his conquest of Wales which he secured by a chain of castles and walled towns. The construction of a new stone Caernarfon Castle seems to have started as soon as the campaign had finished. Edward's architect, James of St. George, may well have modelled the castle on the walls of Constantinople, possibly being aware of the town's legendary associations. Edward's fourth son, Edward of Caernarfon, later Edward II of England, was born at the castle in April 1284 and made Prince of Wales in 1301. A story recorded in the 16th century suggests that the new prince was offered to the native Welsh on the premise "that [he] was borne in Wales and could speake never a word of English", however, there is no contemporary evidence to support this. Caernarfon was constituted a borough in 1284 by a charter of Edward I. The charter, which was confirmed on a number