Prokopios 12 was a subdeacon at Constantinople; he was removed from his position by Ignatios 1 because of his unsuitable character; at the council of Constantinople in 861 he tore off Ignatios 1's omophorion and described him as unworthy: Nicetas, Vita Ignatii 520C (ἐκκήρυκτος ὑποδιάκονος, Προκόπιος τοὔνομα, τὸν λόγον ἄλογος, τὸν βίον βέβηλος). He was therefore subdeacon between 847 and 858.

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