Maria Christina of the Two Sicilies
In the regency of Queen Maria Christina of the Two Sicilies (1833–1840), Mon was appointed for his first high political office, minister of finance from 1837 to 1838, in a moderate cabinet headed by Narciso Fernández de Heredia, 2nd Count of Heredia-Spínola. During the regency of the progressivist Baldomero Espartero (1840–1843), he was in none of the cabinets but remained active in political life.