A favourable wind from the north-east carried the fleet rapidly across the Bay of Biscay, and it proceeded on its way, keeping well out of sight of the coast of Portugal. The three fastest sailers of the fleet were sent on ahead as soon as they rounded Cape St. Vincent, with orders to capture all small vessels which might carry to Cadiz the tidings of the approach of the fleet.

Early on the morning of the 20th June the fleet anchored off the spit of San Sebastian on the southern side of the city.

Cadiz was defended by the fort of San Sebastian on one side and that of San Felipe on the other; while the fort of Pun tales, on the long spit of sand connecting the city with the mainland, defended the channel leading up to Puerto Real, and covered by its guns the Spanish galleys and ships of war anchored there. Lying off the town when the English fleet came in sight were forty richly-laden merchant ships about to sail for Mexico, under the convoy of four great men-of-war, two Lisbon galleons, two argosies, and three frigates.