The name of the author of the anonymous work De politia et disciplina civili et ecclesiastica (1585) was a wellhidden secret for centuries. An attempt is made to solve this mystery. The name of the printer and the place are mentioned: Leonardus Niestus, Lugduni Batavorum. These explicit data do not lead anywhere. The dedication of the work contains valuable information about the author. He is a relative of F. Junius and H. Smetius, professors at Heidelberg University in theology and medicine and married to sisters of the Corput family from Breda. He mentions several times Italy and the Italians as his homeland, where he is not allowed to go. Lastly his initials are given: I.B.A.C. On the basis of recently published dissertations on one of the members of the Corput family and the Italian church in London in the sixteenth century the conclusion can be made that a member of the Corput family originating from Italy is the author. We found Ioannes Baptista Aurellius Calabrensis (ca.1540-1596) member of a Waldense family from the South of Italy. His mother had sent him in 1558/9 to the Academy of Geneva to prepare for the ministry in Italy. The family in Calabria fell victim to the Inquisition in 1561 and I.B.A.C. became a minister in France and subsequently in the small Italian reformed church of London from 1570 till his death in 1596. In London he married a member of the Corput family, Mary, and became related to Junius, Smetius and Emanuel van Meteren, the famous historian. He published two other works, not anonymous, one in Italian. His now forgotten 'De politia' was influential in the Dutch Republic because it was used by J. Wtenbogaert.