The third Battle of Cape St. Vincent saw Admiral Charles Napier commanding British naval forces in a decisive engagement against Dom Miguel, who had seized control of Portugal in a coup. The backdrop of this confrontation was a larger power struggle between liberal forces supporting Dom Pedro IV and conservatives led by Dom Miguel. British interests were aligned with those of Dom Pedro, as they sought to weaken Miguel's grip on Portugal and support the constitutional monarchy. Napier's fleet, well-prepared and strategically positioned, engaged Miguel's forces with superior tactics.

Throughout the skirmish, the British ships demonstrated extraordinary maneuverability and firepower, enabling them to outmatch the Portuguese vessels. The successful engagement not only resulted in a defeat for Dom Miguel's forces but also had broader implications for the balance of power in the region. The victory bolstered the liberal cause in Portugal and simultaneously highlighted the declining influence of Portuguese naval power. Napier's leadership and the British fleet's capabilities were on full display, marking a key moment in naval warfare.

The aftermath of the battle had significant ramifications for Portugal's political landscape. With British support, liberal factions gained momentum against Miguel, fostering a push towards establishing a constitutional monarchy. This influence of foreign powers in Portuguese affairs illustrates the intricate web of alliances and rivalries during the age of imperialism, where naval strength played a crucial role in shaping national destinies.