Gosselyn, Guencelin, Guidelinus, Guitelinus
The Archbishop of London in the fifth century.
When the Romans were departing Britain for good, Guethelin made a rousing speech to the British people in which he encouraged them to develop a national pride, train themselves as warriors, and defend their country. Nevertheless, Britain fell to ruin and was invaded by Huns and Picts, led by Guanius and Melga.
Guethelin traveled to Brittany to seek help. He ordained Constantine, brother of Aldroenus, as King of Britain, and brought him back to the island to drive out the barbarians. After Constantine pacified the land once again, Guethelin raised two of Constantine’s children: Ambrosius Aurelius and Uther Pendragon.
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155
Brut | Layamon, late 12th century to mid-13th century