security of Portugal's overseas empire that was more important than its inland frontier. To protect Portugal's trade routes from South America, the ministers in Lisbon knew the importance of aligning themselves with the dominant naval power in the Atlantic. After Rooke's success at Vigo, it was clear that that naval strength reposed in the Maritime Powers. In May 1703, the Portuguese signed the Methuen Treaties with England. "The preservation of our overseas colonies makes it indispensable for us to have a good intelligence with the powers which now possess the command of the sea," commented José da Cunha Brochado, the Portuguese minister in London, "the cost is heavy, but for us such an understanding is essential." It was an Allied triumph to detach Portugal from her French alliance: with Lisbon as a base the Allied fleet could dominate the Strait of Gibraltar and cripple French action in the Mediterranean. But the alliance with Portugal forced a major change in Allied strategy: the Maritime Powers now found themselves committed to extensive campaigning in Spain, with one army based in Lisbon, another based to the east in Catalonia. The policy was ultimately to prove a heavy burden and the cause of a disastrous campaign in the peninsula, but in the long term, the commercial provisions of the treaties were to prove an essential component of Britain's wealth. The naval victory at Vigo, therefore, made an indirect but powerful contribution to Britain's 18th century prosperity. Sunken treasure Efforts to recover the sunken treasure began almost immediately and continued for centuries. After their initial attempts failed, the Spanish government hired private contractors to recover the treasure, but these also proved unsuccessful. In 1728, a Frenchman named Alexandre Goubert managed to bring a ship almost completely to shore, but abandoned his efforts when it became apparent that it was a French battleship without treasure. An English expedition in 1825 led by William Evans utilized a diving bell, and over the course of a year managed to recover small amounts of silver, cannonballs, and other items. Around the same period, a group calling itself The American Vigo Bay Treasure Company made an ill-fated attempt to raise a ship, tearing it apart. Decades later, Cavalier Pino, using his invention the hydroscope, scanned the location and mapped out several ships, and with a series of careful experiments managed to recover several cannons and preserved wood. On 10 August