Shortly after this ineffectual effort to drive off the blockading squadron, the home-coming Brazil fleet appeared, and, being quite ignorant of the state of affairs, sailed into the hands of Blake and Popham. This was a second and a worse blow to the Portuguese. Once more King John was stirred up to make an effort. Again he appealed to Rupert, and again nothing came of it. The Royalist promised help, but Blake and Popham left him no opportunity of keeping his word. Their ships by this time must have been very foul. They had good reason to be satisfied with the punishment they had inflicted on the King of Portugal, and they sailed with their prizes for the Spanish port of San Lucar de Barrameda. By this time the Portuguese Government had been taught that it was not wisdom to fight with the keepers of the liberties of England. It took advantage of the absence of Blake and Popham to get rid of Rupert, not by driving him out, a feat beyond its resources, but by bribing him to be gone. His ships were refitted, his prizes were taken off his hands, and he was bowed out. Rupert himself was not loth to be at sea again, where there were prizes to be taken. He ran through the Straits of Gibraltar and entered the Mediterranean, with the intention of preying on English commerce.
This third stage of his career began in September 1650. It was a step downwards. By this time the ruin of the Royalist cause had been put beyond doubt. The Governments of the Continent were beginning to grasp the fact that it would be wiser for them to make friends with the new power. A naval force, which no longer represented a Government in possession of even a part of its territory, was on the high road to fall into sheer piracy. It could live only by plunder, and was compelled to treat all who refused to allow it to sell its booty as enemies. In the Mediterranean, Rupert made haste to prove to all the world that he was not the man to stand upon trifles, or to consider those who were not strong enough to inspire him with respect. The extreme feebleness of the Spanish Government was a temptation to a man of his temperament. He took a bold and simple line with the Spanish authority in the southern ports. All English ships, he said, which obey the present revolutionary Government are the property of the rebels. No civilised State can be allowed to harbour such people. Therefore, when I find English ships in your harbours, I shall attack them, and, if you interfere with me, shall fire on you.