His navy work was vital. He was Secretary of the Treasury, War, the Navy, and the Indies during the rule of Ferdinand VI. Among other initiatives, he improved conditions at naval bases and oversaw the construction of the 3 major centers at Ferrol, Cartagena, and La Carraca in a bid to boost shipbuilding. He increased investment in scientific and educational military institutions: a clear sign of a new approach highlighting the importance of science for a nation's development. Together with José Patiño y Rosales and Knight of Malta Antonio Valdés, he promoted a comprehensive naval program, which ranged from scientific training for officers to establishing a significant institutional infrastructure. Under his leadership, important institutions such as the Royal Company of Midshipmen, Naval College of Surgery, and Astronomical Observatory were founded in Cádiz.
The portrait is by an unknown Italian artist and a copy of a work by Venetian painter Jacopo Amiconi, of which an engraving by Manuel Salvador Carmona also exists and can be found at the Prado Museum (G02458). The engraving is based on a drawing by Francisco Javier Ramos Albertos (1744–1817) which is kept at the National Library of Spain (Dib/18/1/7175). In front of a background featuring a curtain and columns with entablature, the Marquis appears half-length, dressed in 18th-century style in a gold-trimmed, blue dress coat with crimson cuffs and vest, and a white silk handkerchief. He wears various insignias in reference to his appointments: the Golden Fleece insignia hangs on his chest and, above it, that of the Order of St John of Jerusalem. He also bears the symbol and badge of the Order of Calatrava, and the insignia and sash of the Order of Saint Januarius.