Sir Gawain and the Green Knight is in some ways a distinctly English poem – in its alliterative metre, for one thing, and also in the north-country settings of events at Hautdesert and the Green Chapel. Yet the main literary tradition to which the poem belongs is to be looked for in France. Although King Arthur was originally an insular, British hero, romances of Arthur flourished first and chiefly across the Channel: in the verse romances of the twelfth-century poet Chrétien de Troyes and in the great prose cycles of thirteenth-century France. It is in a world already largely realized by such Continental predecessors that the Gawain-poet embeds his own story; and there are many things in that world that he simply takes for granted – general conventions of behaviour, and also particular narrative facts. Thus, I believe he would not have expected readers to be at all surprised, as modern ones commonly are, by the explanation that the Green Knight finally offers for the strange events of the Adventure of the Green Chapel. Morgan le Fay, we are suddenly told, devised the whole affair in order to test the Round Table and terrify Guinevere to death, having learned the necessary magic arts during a love-affair with the enchanter Merlin (ll. 2446-62). The hostility of Morgan towards her half-brother Arthur, his knights, and especially his queen was one of the most familiar established facts in French romance, duly explained there on more than one occasion; and marvels such as the Green Knight and his returning head were not infrequently explained by tracing them back, directly or indirectly, to the book-learning of the mysterious Merlin.

It was from French romance, also, that the Gawain-poet derived one of the two main elements in his plot: what is now commonly referred to as the Beheading Game. This bizarre story, in which a man agrees to decapitate a challenger after granting that the challenger may later decapitate him in return, has been traced back as far as an early Irish tale, Bricriu's Feast. Though it is hardly the stuff of which normal knightly adventures are made, the story appears more than once in French romances. Most probably the English poet encountered it in one of the continuations of Chrétien's unfinished Perceval.