In the twelfth and thirteenth centuries, the monarchy had been the great promoter of establishing and developing the Order of St John in the Crown of Castile, granting it several donations and privileges. During this period, the order, on its part, generally acted as an instrument of royal power in Castile. However, by the second half of the thirteenth century, it had gradually begun to lose this royal patronage. 1 It is precisely the purpose of the present paper to focus on the process of readjustment in the relations between the Hospitaller institution and the Castilian monarchy. 2