In spite of the differences that characterized Anglo-Portuguese relations in the nineteenth century, the African imperial interests of Great Britain and Portugal coincided in many important instances. This did not always appear to be the case, however. In fact, up to 1850, relations between the two countries were particularly troubled by Britain's insistence that Portugal should put an end to the slave trade from the Portuguese colonies in Africa to Brazil. Other minor differences placed Portugal and Great Britain at loggerheads in the nineteenth century. They disputed ownership of the small island of Bolama off the coast of Guinea, and of Delagoa Bay. These differences were, however, settled in Portugal's favour by international arbitration and left hardly a mark on diplomatic relations between the two countries.

Another dispute would leave much deeper marks, though. It arose from Britain's objections to the ambitious plans of Barros Gomes, Minister of the Colonies in 1886, who claimed possession of the land stretching between Angola and Mozambique, which would later become Rhodesia, the so-called Rose-Coloured Map. To put an end to his plans, the British government sent the Portuguese government an ultimatum in 1890, and Portugal was forced to back down. The main effect of this incident was to cast a shadow over Portuguese public opinion about the African colonies, and Britain loomed as the great enemy of Portuguese aspirations in Africa. Yet, Portugal's involvement in the question of British political and military power in South Africa shows that Britain was in fact Portugal's best ally.