These are the names of the Isle of Britain

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].

Britain has three chief outpost islands, and twenty-seven are subordinate to it. These are the three outpost islands: Anglesey, Man, and Lundy. It has three chief deltas, and seven score subordinate ones.  And thirty four chief ports, and thirty three chief cities. These are their names: Caer Alclut [Dumbarton]. Caer Llyr [Leicester]. Caer Hawyd. Caer Efrawc [York]. Caer Gent [Canterbury?]. Caer Wyranghon [Worcester]. Caer Llundein [London]. Caer Lirion. Caer Golin [Colchester]. Caer Lloyw [Gloucester]. Caer Gei. Caer Siri. Caer Wynt. Caer Went [Gwent]. Caer Grant [Cambridge]. Caer Dawri [Dorchester]. Caer Llwyd Coet [Lincoln]. Caer Myrdin [Carmarthen]. Caer yn Aruon [Carnarvon]. Caer Gorgyrn. Caer Lleon [Caerleon-on-Usk or Chester]. Caer Gorcon [Worren?]. Caer Cusrad. Caer Urnas [Wroxeter]. Caer Selemion. Caer Mygeid [Meivod]. Caer Lyssydit. Caer Beris [Portchester]. Caer Llion [Chester or Caerleon-on-Usk]. Caer Weir [Warwick]. Caer Gradawc. Caer Widawl Wir [St. Albans].

SOURCE:

Trioedd Ynys Prydein. ed. and trans. Rachel Bromwich. Cardiff: University of Wales Press, 1961.