[Belinus] summoned workmen from all over the island and ordered them to construct a road of stones and mortar which should bisect the island longitudinally from the Cornish sea to the shore of Caithness and should lead in a straight line to each of the cities on the route. He then ordered a second road to be built, running west to east across the kingdom from the town of St Davids on the Demetian Sea over to Southampton and again leading directly to the cities in between. He built two more roads in a diagonal pattern across the island, to lead to the cities for which no provision had been made. Then he consecrated these highways in all honour and dignity, proclaiming it to be an integral part of his code of laws that punishment should be meted out to any person who committed an act of violence upon them. If anyone wishes to know the full details of the highway code established by Belinus, he must read the Molmutine Laws which the historian Gildas translated from Welsh into Latin, and which King Alfred later rewrote in the English language. [III.5]

ST DAVID'S is, Geoffrey tells us, one end-point on the east-west road built by Belinus across his kingdom. Tatlock remarks that there never was a main road between SOUTHAMPTON and St David's, though St David's is indeed a logical choice because of its position in the far west (p. 67). Geoffrey makes it an invasion point on one occasion:

Gillomanius took pity on Paschent when the latter explained his misfortune. He promised Paschent help and himself complained of the injury which Uther, the brother of Aurelius, had done him, too, by coming to seek the Giant's Ring. A treaty was agreed upon between them. They fitted out ships, went on board and then landed near the town of Menevia. As soon as this was known, a force of armed men was assembled and Utherpendragon set off for Kambria to fight them. [VIII.14]

The area was indeed subject to raids from the sea, between 645 and 1097. Menevia was attacked and destroyed many times: the present cathedral was begun in 1181 (visit St Davids Cathedral for more information). The monastery is said to have been founded by St David (d. 589), though in Geoffrey's account, the foundation is attributed to Patrick:

It was then, too, that David, most holy Archbishop of the City of the Legions, died in the town of Menevia, inside his own abbey, which he loved more than all the other monasteries of his diocese, for St. Patrick, who prophesied David's own birth, had founded it. He was seized by some sudden illness and died while on a visit to his friars there. He was buried in that same church, on the order of Mabgo, King of the Venedotians. [XI.3]

Tatlock suggests that Geoffrey was slighting St Davids' claims to episcopal supremacy, which had been advanced repeatedly from 1125 onwards (p. 67).

Menevia shall be dressed in the pall of the City of the Legions, and a preacher from Ireland shall be struck dumb by a child still growing in the womb. [VII.3]

This prophecy suggests that St Davids will assume episcopal supremacy from CAERLEON.

The National Library of Wales has digitized the Collectanea Menevensia, a history of the parish dating to 1820.