Feliú oversaw the cession of Florida to Great Britain by the Treaty of Paris on July 21, 1763 and the subsequent immigration of most of the province's Spanish and African inhabitants to Cuba.
Following the war between Spain and England, which had revealed the vulnerability of Florida to an English attack, Feliú sought to improve the military readiness of the province.
Feliú had the thick forest between Fort Mose and St. Augustine cut down to deprive the Native Americans of cover to launch their raids, saving five thousand suitable logs to use as stakes in constructing fortifications.
Castelló and mission engineer Juan de Cotilla, who had returned to Florida in 1763, became important Spanish architects in the region.
[5] The official ceremony took place at the Castillo de San Marcos, where he delivered the city keys to Major John Hedges, the ranking representative of King George III.