“Pedigree”–“Sir Eglamore of Artoys” originated in France, and the earliest surviving translation dates from the mid-fifteenth century (an imperfect copy in the Thornton Manuscript, and a complete edition at Cambridge). Sixteenth century printings were made, undated, by William Copland and John Walley, and there are surviving copies of each (Copland’s in the Bodleian, Walley’s in the British Museum).
Furnivall summarized the tale so concisely, I transcribe the excerpt here in its entirety from his “Captain Cox: His Books and Ballads”:
“…how the poor knight Sir Eglamore loves Christabel, the fair daughter of the Earl of Artoys, and how he undertakes three Deeds of Arms to win her; how accordingly he kills the giant Marrocke and a big Boar, a second Giant, and a Dragon near Rome; how before marriage he begets a boy on Christabell, with which, when born, she is put out to sea alone in a ship, and a Griffin flies away with the boy. She is driven to Egypt, her boy carried to Isarell, while Eglamore, mourning them both as lost, fights and dwells for 15 years in the Holy Land. Then his son, Degrabell, wins his own mother Christabell at a tournament, and weds her; but before the marriage is consummated she discovers that Degrabell is her son, and their marriage void. At the second tourney, Eglamore wins his Christabell; they marry; and rule Artoys.
Both Furnivall, and James O. Halliwell (editor of “The Thornton Romances” below) make reference to another title, “Torrent of Portugal” as containing many common elements / being another version of the same tale.
Google books has a copy of Halliwell’s “Thornton Romances”, of which the version of “Sir Eglamore” selected was the Cambridge manuscript referenced above.