Sire de la Noire Espine
A nobleman who owned a piece of land in Arthur’s realm. When he died, his eldest daughter disinherited his youngest daughter and expelled her from the land.
The younger daughter traveled to King Arthur’s court to appeal the case. Yvain agreed to champion her cause, and Gawain was assigned as the eldest daughter’s champion. After fighting for many hours, the two knights revealed their identities to each other, and both stopped fighting immediately. They both appealed to Arthur to award the judgment to the other. Arthur, recognizing that their self-sacrifice was a sign of love for each other, made an independent judgment in the case, awarding half the land to the wronged younger daughter.
Source
Yvain, or Le Chevalier au Lion | Chrétien de Troyes, late 12th century