Sutton remained in the Mediterranean with Nelson's fleet, initially patrolling off Toulon, before transferring to Cadiz. On 3 October 1804 "Amphion" was one of four frigates sent to intercept four Spanish frigates approaching Cadiz with a large cargo of specie. The British ships, consisting of "Amphion", , and , sighted the Spanish early on the morning of 5 October, and gave chase. The Spanish were hailed, but refused to surrender to the British, and fighting broke out. After a short but fierce action, one Spanish ship blew up and the other three struck their colours. The "Amphion" had three wounded in the action. The treasure recovered from the three surviving ships was valued at £1,000,000, but its seizure contributed to the Spanish decision to ally with France and declare war on Britain.