To be blunt, there was almost no real title of 'Spymaster' in any court in medieval Europe, in part due to practicality ('Who's that man over there? Oh, he's Roger de la Pole, the Spymaster? Best keep my mouth shut then') and in part due to the culture of Western Europe. Furthermore, sources for medieval spymasters can be an absolute pain to find. While letters, such as those exchanged between William Montagu and Edward III before the deposition of Roger Mortimer, do hint strongly at certain individuals who temporarily act as collectors of information, we can find just about bugger all for anything resembling an appointment.

For example, who informed Louis VII of his ex-wife's marriage to King Henry II of England? A messenger, almost certainly. We have no evidence of some spider-like manipulator who discerned that Henry and Eleanor were in talks. Indeed, the act of intelligence gathering was fundamentally decentralised beneath the level of the royal court. Certain lords would have contacts in certain places; William Marshal had significant estates in Longueville, for example, and if any news reached him from his contacts in Melun or Paris, he'd have likely passed that on directly to the king.

Speculation is all we really have, until maybe the late 1400's, where many people end the medieval period. John Morton was tasked by Henry VII to seek out information and report directly to him. Francis Walsingham acted as principal secretary to Elizabeth I, and pretty much filled the capacity of spymaster.

But think of it in this way aswell; if you were a medieval nobleman, steeped in chivalry, would you really want to be the man responsible for all your monarchs underhanded dealings? Imagine both the power he could wield, and the risks to his person. He would have to be fanatically loyal to his ruler, and able to deal with the constant suspicion of his contemporaries. It would be a highly dangerous and impractical position.