Archaeology has failed to reveal a British settlement pre-existing Roman London. Judging by the number of votive deposits found in the Thames and it tributary waters the area must have been a liminal zone sparsely populated by the native population. Debate continues as to why the Romans founded Londinium where they did.
Many archaeologists favour the origin of the town as a settlement of merchants and officials planted on the north bank of the Thames some years after the Roman conquest, emerging as a major commercial centre during the 1st century AD. The Roman City of London developed on two previously unoccupied hills; Cornhill and Ludgate Hill, the site of St Paul's Cathedral. Between the two flowed the sacred waters of the Walbrook.
In 2006 archaeologists from the Museum of London discovered a series of ditches, the western boundary of a double-ditch enclosure on the east bank of the Walbrook, which has been interpreted as evidence of the first, short-lived London fort; the latest wisdom being that London appears to have first emerged as a frontier port, where Claudius amassed his army in 43 AD before the advance on Colchester some 60 miles to the north-east.
The earliest Arthurian associations with the City of London are found to be limited to the Mabinogi tale Brânwen Daughter of Llyr and the ancient Celtic cult of the Living Head. Now we turn to two influential medieval insular writers and their storytelling of Arthurian London who place their tales in two distinct parts of the capital; a tale of two cities.
Sir Thomas Malory on occasion has Arthur located near Westminster in London but, like Geoffrey of Monmouth some three hundred and thirty years before him, fails to make the city the centre of Arthur's rule. Malory has his Camelot based at Winchester but the most famous Arthurian event in London is the drawing of the sword from the stone.
Geoffrey of Monmouth consumes most of his writing on London with the earlier Brutus dynasty who he claims established a pre-Roman settlement on the banks of the Thames. It is apparent that Geoffrey has in mind the early Roman settlement as he has the city walls subsequently refortified by King Lud. Later, he has the Britons loosing London to the Saxons before recapturing it. Geoffrey has Arthur hold the first council of his reign in London but fails to mention any further visits to the city by the King.
Book the First: The New Troy
In his 12th century 'pseudohistorical' work Historia Regum Britanniae (History of the Kings of Britain) Geoffrey, following the outline story contained in the Historia Brittonum, narrates the history of the British Kings up to Cadwaladr (ap Cadwallon), the last of the line that began with Brutus of Troy.
Geoffrey names London as one of the three noblest cities along with York and the City of the Legions (Caerleon-on-Usk), calling these the seats of the three Archflamens. By this term Geofffrey probably meant pagan Arch-Druids who, after “being delivered from idolatry, where made Archbishops”. [Book IV, Chap. 19]  Geoffrey has Vortigern take Constans to London to be made King. Following the slaughter of the British princes at the temple of Ambrius (Stonehenge) on the kalends of May, Vortigern grants all of the Saxon's demands. They take London, before advancing on York, Lincoln and Winchester. Vortigern retired to Cambria (Wales) and consulted his wise men.
Geoffrey is clearly influenced here by the story contained within the anonymous 9th century Historia Brittonum.  Vortigern is advised by his twelve wise men to retire to the remote boundaries of his kingdom and build a citadel; but three times the building collapsed. To make the fortress stand up Vortigern was advised to: “find a child born without a father, put him to death, and sprinkle with his blood the ground on which the citadel is to be build”. The boy Ambrose is brought to Vortigern who explains that the fortress will not stand because it is sighted above a subterranean pool containing two dragons, one red, the other white. This first account of the boy Ambrose (also known as Emrys) is without doubt a contributory inspiration in Geoffrey's later creation of Merlin and his apparent obsession with the art of prophecy.
|Vortigern and Merlin by Alan Lee|
However, the tale of 'Lludd and Llefelys' was omitted by Geoffrey from his original Latin chronicle but is included in several Middle Welsh versions of his work known as Brut y Brenhinedd (Chronicle of the Kings), collectively known as the Brut, (a chronicle commencing with Brutus) in which the redactor would make minor corrections to errors possibly occurring in translation or additions appertaining to local tradition. The presence or absence of the tale of 'Lludd and Llefelys' has been used to classify the early versions of the Brut, with the tale being included for the first time in the mid-13th century manuscript Peniarth MS 44.
However, the tradition of Brutus as founder of Britain is older than Geoffrey's History of the Kings of Britain and appears for the first time in the 9th century Historia Brittonum, clearly one of Geoffrey's main sources. Yet despite figuring so prominently in the Historia Brittonum, Brutus failed to make a major impact on Welsh tradition and according to material pre-dating Geoffrey, after conquest the Island of Britain was named after Prydein son of Aedd Mawr.  Yet we find that no genuine tradition of Prydein has survived and he is more elusive than Brutus.
In describing the origins of the Britons, the Historia Brittonum states that the island of Britain derives its name from Brutus, “a Roman consul who conquered Spain, and reduced that country to a Roman province. He afterwards subdued the island of Britain, whose inhabitants were the descendants of the Romans, from Silvius Posthumus.” After the Trojan war Aeneas arrived with his son in Italy and obtained the kingdom of the Romans. Aeneas was the father of Ascanius and Silvius, the latter was called 'Posthumus' because he was born after the death of his father. 
Aeneas, having been informed that his daughter-in-law was pregnant by Ascanius ordered his son to send his magician to examine her and find out whether the child were male or female, but in so doing the wizard also foretold of a tragedy. The grandson of Aeneas was named Brutus who, in fulfilling the wizard's prophecy, killed his father Ascanius. He was driven from Italy and after some time in Gaul “came to this island which is named Britannia from his name.” The Historia Brittonum provides a second account of Brutus: “after the deluge, the three sons of Noah went to three different parts of the earth: Asia, Africa, and Europe. The European was Alanus, with his three sons, Hisicion, Armenon, and Neugio. Hisicion had four sons: Froncus, Romanus, Alamanus, and Brutus from which the Britons were so named.” 
In his History of the Kings of Britain, Geoffrey, as was his way, elaborates on the story, but ignored the second account of Brutus from the Historia Brittonum. He has Brutus as Aeneas's great-grandson, whereas the anonymous author of the Historia Brittonum has him as either the grandson then later his great-great-grandson. Aeneas, an important figure in Greek and Roman legend, is a character from Homer's Iliad. Aeneas's journey from Troy and the founding of a enclave south of Rome, is recounted in Virgil's Aeneid. He is one of the few Trojans not to have been killed or enslaved during the fall of Troy. Geoffrey, clearly influenced by the description of the Trojan diaspora in the Aenid, extends this to northern Europe and incorrectly claims Homer as a source for Brutus' foundation of the city of Tours.
Geoffrey has Brutus depart from Greece and arrives to an uninhabited island called Leogecia. At a desolate city on the island they come across a temple of Diana. Brutus consults a statue of the goddess and then falls asleep in front of the altar. During his sleep the goddess comes to him and foretells that he should go to an island in the western sea which was once possessed by giants, and there raise a second Troy.
After a detour through Gaul and meeting up with a second group of Tojans led by Corineus, Brutus arrives on the coast of the promised land at Totnes. The island was called Albion and inhabited by none but a few giants as the oracle had foretold. After driving the giants into the mountains Brutus then named the island 'Britannia' after himself. He came to the river Thames and then built his city, the New Troy: Trinovantum. Corineus and his followers go on to found Cornwall. Brutus's sons Locrinus, Kamber and Albanactus provide names for England (Loegria), Wales (Kambria) and Scotland (Albania), respectively. Brutus's three sons appear to be entirely Geoffrey's creation as they are found in no other source pre-dating his work. 
And, so Geoffrey's story goes, that at the time of the Roman invasion of Britain, Lud became King and rebuilt the city that King Brutus the Trojan had founded and had named as the New Troy (Troia Nova), which according to Geoffrey was the original name of Trinovantum, no doubt influenced by the name of the home of the Trinovantes, one of the Iron Age tribes of pre-Roman Britain, whose homeland was on the north side of the mouth of the Thames, south of the lands of the Iceni. The Trinovantes were considered the most powerful tribe in Britain shortly before Julius Caesar's expeditions into Britain in 55 and 54 BC. Their name is thought to mean "very new" in the sense of "newcomers" and has nothing to do with ancient Troy.
|London Wall, Cooper's Row|
Lud’s name persists in present day Ludgate Circus and Ludgate Hill, on which St. Paul's Cathedral now stands, Ludgate being a major gateway into the old City of London. Crumbling statues of King Lud and his two sons, Androgeus and Tenvantius, which formerly stood at the gate, now stand in the porch of the church of St Dunstan-in-the-West on Fleet Street in London. At one time there was even a public house at Ludgate Circus called the "King Lud".
Yet the etymology of the name of England's capital city remains a mystery and probably derives from something similar to the original name of modern day Lyon in France: Lugdunum, named after the ancient pan-Celtic deity Lugus, of which Lud(d) is a Welsh variant.
Legend claims that King Lud was buried in an entrance to the city that still bears his name, Ludgate, his father Beli Mawr supposedly buried at Billingsgate and the legendary burial place of King Brutus is Bryn Gwyn, the White Mount, at the site of the Tower of London. It is here, according to the Mabinogion, that they buried the head of Brân after the ill-fated journey to Ireland in which none save seven returned.
Next: Book the Second: The 'Knyght Presoner'
Notes & References
1. John Michell, The Traveller's Guide to Sacred England, Gothic Image, 1996.
2. Geoffrey of Monmouth, Historia Regum Britanniae ("History of the Kings of Britain"), c.1136.
3. Later editions of the Historia Brittonum are often ascribed to a 'Nennius', however, the earliest version dated to c.829/830 AD remains anonymous.
4. Rachel Bromwich, Trioedd Ynys Prydein: The Triads of the Island of Britain. University Of Wales Press, 2006.
5. Bromwich, Ibid. The Names of the Isle of Britain (Enweu ynys Prydein) - “The first name that this island bore, before it was taken or settled: Myrddin's Precinct. And after it was taken and settled, the island of Honey. And after it was conquered by Prydein son of Aedd Mawr, it was called the Isle of Prydein (Britain).”
6. John Morris, ed. and trans., History of the British (Historia Brittonum), in Nennius: British History and the Welsh Annals, Phillimore, 1980.
7. Morris, Ibid.
8. Karen Jankulak, Geoffrey of Monmouth, University of Wales Press, 2010.
9. Jankulak, Ibid.
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