At the expiration of the prescribed term Mantino found an influential protector in another of his patients, Teodoro Trivulzio, marshal of France and governor of Genoa; the latter, urging his own services to the Venetian Republic, insisted that the council should make the exemption perpetual.
The efforts of Henry VIII of England to get rid of his wife Catherine on the pretext that their marriage was contrary to the Biblical law, and that the dispensation obtained from Pope Julius II was invalid, involved Mantino in difficulties.
Henry sent Richard Croke to Italy in order to obtain opinions favorable to his case, and the latter addressed himself to Jewish as well as to Christian scholars.
This decision created for Mantino many enemies in Venice, where Croke had won a favorable opinion from the famous physician and scholar Elijah Menahem Halfon, among others.
This high position did not prevent Mantino from concerning himself with the affairs of the Jewish community of Rome, in whose records he appears as a member of the rabbinate, with the title "gaon."