Prior to Ithaka he was a financial, commodity and risk manager at the Economic-Financial department of Naturgy, a listed utility firm based in Spain. Before his time at Naturgy, Guillermo worked at the Economic-Financial shared services center and worked as consultant for Soluziona, an independent advisory firm based in Madrid (Spain).

He holds an MBA from IE and a Master’s degree in Law and a Diploma in Economics from the University of Deusto (Spain).