Tales of King Arthur date back as early as the 6th century AD, and long before Lancelot was the best knight of the Round Table, Gawain was Arthur's most fiery champion. Here is a paragraph translated from Latin from Geoffery of Monmouth's Historia Regum Britanniae (written in 1136) that describes the battle between Gawain and the emperor Lucius in Arthur's war against Rome:
"Gawain ... by hewing down troops, as has been told, found at last the opportunity he wanted and attacked the Roman commander and engaged with him directly. But Lucius, vigorous with youth, had much bravery, much energy, much valor, and he desired nothing more than to encounter a soldier who forced him to test what he could do in arms. Confronting Gawain therefore, he was glad to enter combat with him, and he gloried, for he had heard so much of Gawain's great fame. As the battle was long waged between them, they dealt powerful blows, extending their shields against the attacks, and each labored to bring on the death of the other."