Romance of Horn is an Anglo-Norman literature romans d'aventure ("adventure story") tale written around 1170 by an author apparently named "Thomas".
[1] The story became the basis for one of the earliest Middle English romances, King Horn, written around 1225.
The hero, named Horn, is the son of the king Aälof of Suddene (probably somewhere near Devon).
He and twelve companions then set sail in a boat only to end up on the shores of Brittany, where he grows to manhood and falls in love with the king's daughter Rigmel.
There he defends the kingdom from invading Saracens, but the king banishes him to Ireland after he is wrongfully accused of trying to usurp the throne.