I know the sizes of medieval fiefs were probably all over the place, but at what point would a medieval nobleman’s holdings qualify him to be a “Big Deal” in a kingdom’s politics? 100 sq. km? 1,000 sq. km? 2,000 sq. km? What was usually the cutoff to be considered a full on magnate? And how does that compare with the estimated size of the fiefdoms in Westeros?

Well, it’s not just about size – especially because fiefdoms were often non-contiguous, which makes square mileage difficult to compute. 

Take Edward IV, for example, who at the moment of his accession to the throne, was Duke of York, Earl of March (and

and Baron Mortimer of Wigmore), Earl of Cambridge, Earl of Ulster, Lord of Clare. To give you an idea of how crazy all over the place this was, let me show you on the map:

So that’s Ireland, Wales, Northern England, and Southeast England. At that level, it’s really not about square mileage it’s more about prestige, influence, income, and military manpower.