Question: Which Earl allegedly founded the English colony granted land by the Byzantine Emperor Alexius I Comnenus?
Sentence (from "Játvarðar Saga"): Among the various details contained in the saga, there is an account of the origin of an English colony in the Black Sea founded by one "Siward earl of Gloucester" ("Sigurðr jarl af Glocestr"), a refugee of the Norman Conquest of England.
Relevant evidence: Yes