This is one of the most famous stories in Arthurian folklore. It may well be a symbolic representation of the transfer of sovereignty to Arthur after the death of his father whose name appears in HG 2a as Petr. Latin ‘petra’ means ‘rock’. Drawing of the sword could only be achieved by the rightful claimant, that is Uthr’s true heir. Although it first appears in Robert de Boron’s Merlin this interpretation indicates the story may well have an older origin.
HB 41 refers to a site called Campus Elleti:
“As they explored all the provinces they came to the plain of Elled in the country called Glywysing.”
where the envoys found what they were searching for, a child without a father. His name was “Ambrosius”, that is “Embreis Guletic”. The answer to the question of who the plain was named after can be found in JC 4 which consists of three parts:
||JC 4b||JC 4c seg.|
|-4||Owain Finddu||Constantinus||Owain Finddu|
|-5||Macsen Wledig||Magnus Maximus||Macsen Wledig||Ceindrech|
|-8||Cynan||Constantius Chlorus||Elen Luyddog||Morddu|
JC 4c mentions the individual, Eledi ap Morddu, as a grandfather of Ceindrech, a wife of Macsen Wledig and mother of Owain Finddu. JC 4a shows Glywys, the eponym of Glywysing, as a descendant of Owain.
The Liber Landavensis mentions the name “Elleti” and the place is located near “Llansanwyr”, that is Llansannor. It may be significant that the village is less than 3 miles distant from Llanillid. There was a chapel dedicated to St. Ilid on Tintagel island.
 Davies, W., 1979, 98.