I am of course aware that there were other influences on Scott besides medieval literature and that sometimes there are alternative sources for a particular motif or detail or point of style. I cannot always pin Scott down to a medieval source to the exclusion of other possible sources. In such cases it is altogether conceivable that three or four or more literary works from different periods of literary history were on his mind at the same time. If so, I am inclined to believe that medieval romance weighed most heavily because of his utter fascination with literature of this sort during his formative years. Although he also read widely in other literature at an early age, ballads and old romances were his passion. ...I point out what Scott has borrowed and show how he has used the borrowing. When he has covered his tracks, I cannot always say which romance is involved... but the accumulation of interesting parallels provides good circumstantial evidence in support of my belief that medieval romance is the most important source for the Waverly Novels.
Walter Scott