And in the Enterprise there had seemed to be in victory a risk even greater than in defeat. If Mary Stuart was alive when his armies overthrew the English she would have to be Queen of England. She was a Catholic, at least. She had courted him of late and she might prove grateful. But her heart was French, and Philip had learned from his father that the gravest danger to their dynasty lay in a union of France and England. It would be a bitter irony if Spanish blood and Spanish treasure were to be spent only to make the King of France again the greatest king of Europe.

Garrett Mattingly, The Defeat of the Spanish A…, loc. 179