At the end of Gawain and the Green Knight (Weston's translation) says to Gawain
"Bernlak de Hautdesert am I called in this land. Morgain le Fay dwelleth in mine house, and through knowledge of clerkly craft hath she taken many. For long time was she the mistress of Merlin, who knew well all you knights of the court. Morgain the goddess is she called therefore, and there is none so haughty but she can bring him low. She sent me in this guise to yon fair hall to test the truth of the renown that is spread abroad of the valour of the Round Table. She taught me this marvel to betray your wits, to vex Guinevere and fright her to death by the man who spake with his head in his hand at the high table. That is she who is at home, that ancient lady, she is even thine aunt, Arthur's half-sister, the daughter of the Duchess of Tintagel, who afterward married King Uther. Therefore I bid thee, knight, come to thine aunt, and make merry in thine house; my folk love thee, and I wish thee as well as any man on earth, by my faith, for thy true dealing."
This seems to be quite a cordial attitude, considering that the two have been acting as foes for the entire tale up until this point. I initially read Tolkien's translation, and interpreted it as saying that Morgain bewitched Bernlak (also called Bertilak) and kept him under a spell. However, it Bernlak's actions here suggest that he is no longer under such a spell, as he voluntarily gives away the information. At the same time, it seems odd that he would willingly carry out Morgain's wishes, as he seems to bear no enmity towards Guinevere or Arthur, nor could easily profit.
Was the Green Knight willing to fight Gawain, or was he forced to under a spell?