As there is no historical authority for the events of the celebrated Ballad on which this Tragedy is founded, I have fixed upon the thirteenth century for the period of their occurrence. At that time the kingdom of Castille had recently obtained that supremacy in Spain which led, in a subsequent age, to the political integrity of the country. Burgos, its capital, was a magnificent city; and then also arose that masterpiece of Christian architecture, its famous Cathedral.
This state of comparative refinement and civilization permitted the introduction of more complicated motives than the rude manners of the Ballad would have authorised; while the picturesque features of the Castillian middle ages still flourished in full force; the factions of a powerful nobility, renowned for their turbulence, strong passions, enormous crimes, profound superstition.
-- Benjamin Disraeli, London: May, 1839