At about eight o'clock on the evening of 15 October 1799, the British 38-gun frigate Naiad, under the command of Captain William Pierrepont was patrolling off the North Western coast of Spain when she sighted two enemy frigates, apparently Spanish, to which she gave chase throughout the night. At about three-thirty the following morning, Pierrepont sighted a third ship but she proved to be another British frigate, the 38-gun Etahlion, which immediately joined in the pursuit. As dawn broke, two more British frigates, the Alcamene and the Triton, both 32-guns, appeared on the scene and signalled their willingness to join Pierrepont's squadron. The enemy vessels -by now positively identified as Spaniards- decided to separate in an attempt to outrun their pursuers so Ethalion was ordered after the first and brought her to action after several hours. She proved to be the Thetis and, when captured after a short running fight of only an hour, was found to be carrying cargo of Mexican specie worth just over #300,000. The other Spanish frigate turned south with the three British vessels in close pursuit, but was eventually caught amidst rocks at the entrance to Muros Bay, just below Cape Finisterre, the next morning. When captured, the Santa Brigida was also found to be carrying bullion which, when added to that recovered from the Thetis, exceeded #1 million making the two ships amongst the most valuable prizes ever taken by the Royal Navy.