The three Vaglianos reached their apogee as an international trading company during the 1860s-1880s. It is during this time that they opened the path of the Greeks to global shipping, and made maritime and commercial transactions on an equal basis with the world’s best; in 1881, in London they had a turnover of about £8 million sterling when Schröders had a turnover of £4 million and Rothschild’s £12 million. This chapter analyzes the functioning of their international trading house in trade, finance, and shipping. During the 1850s-1880s, the Vaglianos became the leading international trading house of the Greek entrepreneurial network. In 1858, following the tremendous profits the House enjoyed after the Crimean War, Panagi Vagliano went to the City of London, a move that proved to be decisive. Their activities in banking and particularly the legal confrontation Vagliano vs. the Bank of England illustrates the importance of the Vagliano Brothers in the City of London and its institutions, and investigates the dynamic interrelationship between the foreign City merchant bankers and the development of financial institutions like the bill of exchange.