On October 3rd, the British frigates Indefatigable, 44, Captain Graham Moore, Lively, 38, Captain Graham Eden Hamond, Medusa, 32, Captain John Gore (2), and Amphion, 32, Captain Samuel Sutton, assembled off Cadiz, whither they had been ordered to intercept four Spanish frigates laden with treasure, which were due to arrive from Montevideo. Of the British frigates, the first two were from Cornwallis's fleet, and the last two from Nelson's. The latter Admiral, with his usual judgment, had despatched also the line of battleship Donegal, 74, wishing to make the British force so strong that resistance to it would be hopeless. Unhappily she failed to arrive in time, and there was much unnecessary waste of life. Spain was nominally at peace with Great Britain, though she was at that very moment paying to France a large subsidy, which was, of course, used against England. The treasure expected in the Spanish frigates was therefore destined to be employed by an enemy. But no notice of our intention was given to the Spanish Government and a British officer, Captain Sir Robert Barlow, Kt., was actually on his way in the Triumph, 74, to Cadiz, to pick up and convoy home the British traders who had gathered there. These circumstances led what followed to be severely denounced both at home and abroad.

On the 5th, the Spanish vessels came into sight. They were four in number, the Fama, 34, Medea, 40, Rear-Admiral Don Jose Bustamente, Mercedes, 34, and Clara, 34, a squadron much weaker in force than the British quartette, and suffering the great disadvantage of being taken unprepared. They formed line of battle in the order given above, whereupon the Medusa, the leading British ship, placed herself upon the Fama's weather beam, and the Indefatigable, Amphion, and Lively also paired off with their antagonists in order, the Lively taking her position to leeward, abeam of the last Spanish ship. Captain Moore, the senior British officer, then hailed the Spanish admiral to shorten sail, and, as no reply was made, fired across his ship. The Medea shortened sail, and a boat was sent from the Indefatigable urging Bustamente to allow his squadron to be detained without bloodshed. Honour compelled him to refuse, whereupon the Indefatigable fired a shot across his bows and closed. The Mercedes promptly fired into the Amphion; the Medea fired into the Indefatigable; and the British senior officer made the signal for close action. In ten minutes the Mercedes blew up; in half an hour the Medea and Clara struck their flags. The Fama attempted to escape, and gained on the Medusa, but the Lively was despatched to join in the chase, which was overhauled and captured, with the help of the Medusa, early in the afternoon. The boats of the other British ships, having secured the Medea, turned their attention to the unhappy survivors of the Mercedes. One officer and 45 men were saved, but with that exception, all on board, including several women and children, perished. The prizes had cargoes of great value, in addition to specie, on board, and their total worth was placed at about 1,000,000. In the Mercedes, one-third as much more was lost. The British casualties were only 2 killed and 7 wounded. The Spaniards lost 20 killed and 80 wounded, besides those who perished in the Mercedes.