Enter 1981 and 1984 was dean of the Faculty of Arts of the University and later served as director of its Department of Medieval History.
Under his tutelage was formed a generation of prestigious medievalists, including María Isabel del Val, Juan Carlos Martín Cea, Asunción Esteban Recio, Ángel Martínez Casado and Juan Antonio Bonachía Hernando.
On November 16, 2001, he was elected a full member of the Real Academia de la Historia, to fill the vacancy left by Pedro Lain Entralgo, entering the same in June 2002.
He was one of the largest and most prestigious specialists from Spain in the late medieval period in the Crown of Castile.
In February 2002 he received the honor of Castile and León Award for Social Sciences and Humanities "in recognition of research work on the medieval past, and permanent teachers and generous disposition".