From the pictures of Coca castle on this web site, it can be seen that the project to build it must have been undertaken by a very powerful person. Such a person was Don Alonso de Fonseca, Archbishop of Seville. He was a major figure at the court of Castile. Don Alonso was born in 1418 and died at Coca castle in 1473.

Don Alonso had been appointed Bishop Avila at the age of 27 and Archbishop of Seville at 35. Most of his time was taken up with intrigues at court rather than with church matters. At that time during the reign of Henry IV, Castile was frequently in turmoil and Don Alonso was usually involved in some way. It was at Coca that he built the castle which served both as his residence and a refuge from his enemies.