"Guipuzcoano" was sailing as the flagship of Commodore Don Juan Agustín de Yardi, and commanded by Captain Don Tomás de Malay, in late 1779, escorting a convoy of 15 merchants of the "Guipuzcoan Company of Caracas" from San Sebastián to Cadiz. Also escorting the convoy were four company frigates, the 32-gun "San Carlos", 30-gun "San Rafael", 28-gun "Santa Teresa" and 26-gun "San Bruno", and two smaller vessels, the 16-gun "San Fermín" and 10-gun "San Vicente". On 8 January 1780 the convoy encountered a large British fleet off Cape Finisterre under Admiral Sir George Rodney, bound for the relief of Gibraltar. Rodney closed on the convoy, the copper sheathing on some of his ships allowing them to outsail the Spanish. The whole convoy was captured, with vessels which had been carrying naval stores to the Spanish fleet at Cadiz, and baled goods for the Royal Caracas Company being sent back to England, escorted by and . Those Spanish ships that were found to be carrying provisions were taken to Gibraltar by Rodney, and used to relieve the British forces there.