 The exact date is uncertain, as are the name of who commissioned it and the circumstances of its foundation.According to some scholars San Lorenzo was erected to coincide with the “Basilica Portiana”, which was built by the “Augustus of the West” (Valentinian I or Valentinian II) to please the Bishop of Milan Auxentius (355–372) of the Arian faith.If this is true, San Lorenzo would have preceded the foundation of the four Ambrosian basilicas.