The Anglo-Portuguese Treaty of 1891 was an agreement between Great Britain and Portugal which fixed the boundaries between the British Central Africa Protectorate, (now Malawi) and the territories administered by the British South Africa Company in Mashonaland and Matabeleland (now parts of Zimbabwe) and North-Western Rhodesia (now part of Zambia) and Portuguese Mozambique, and also between the British South Africa Company administered territories of North-Eastern Rhodesia (now in Zambia), and Portuguese Angola.
This treaty brought to an end over 20 years of increasing disagreement over conflicting territorial claims in the eastern part of Central Africa, where Portugal had long-standing claims based on prior discovery and exploration but where British citizens set up missions and embryonic trading concerns in the Shire Highlands in what is now Malawi from the 1860s. These disagreements were increased in the 1870s and 1880s, firstly by a dispute over a British claim to part of Delagoa Bay and by the failure of bilateral negotiations between the two countries over the boundaries of Portuguese territories and secondly as a result of the Berlin Conference of 1884–85, which set-out the doctrine of effective occupation. After the Berlin Conference, Portugal tried to establish a zone of effective occupation linking its colonies in Angola and Mozambique through expeditions making treaties that would establish protectorates over local peoples and obtaining recognition from other European powers. The relative success of these Portuguese efforts alarmed the British government of Lord Salisbury, which was also under pressure from missionaries in the Shire Highlands, and also Cecil Rhodes, who founded the British South Africa Company in 1888 with the aim of controlling as much of south-central Africa as it could. For these reasons, and in response to a minor armed conflict in the Shire Highlands, Lord Salisbury issued the 1890 British Ultimatum which required Portugal to evacuate the areas in dispute. Lord Salisbury refused the Portuguese request for arbitration and, after an abortive attempt to fix the boundaries of their respective territories in 1890, the Anglo-Portuguese Treaty of 1891 was accepted by Portugal under duress.
Origins of the Anglo-Portuguese conflict
At the start of the 19th century, effective Portuguese governance in Africa south of the equator was limited, in Portuguese Mozambique to the Island of Mozambique and several other coastal trading as far south as Delagoa Bay, and in Portuguese Angola to Luanda and Benguela and a few outposts, the most northerly of which was Ambriz Portugal had occupied the coast of Mozambique from the 16th century, and later initiated the Prazo system of large leased estates under nominal Portuguese rule in the Zambezi valley. By the end of the 18th century, the valleys of the Zambezi and lower Shire River were controlled by four families that claimed to be Portuguese but which were virtually independent, and from 1853 the Portuguese government embarked on a series of military campaigns to bring these under its effective control. In the second half of the 19th century, various European powers had an increasing interest in Africa. The first challenge to Portugal's wider claims came from the Transvaal Republic, which in 1868 claimed an outlet to the Indian Ocean at Delagoa Bay. Although in 1869 Portugal and the Transvaal reached agreement on a border under which all of Delagoa Bay was Portuguese, Britain then lodged a claim to the southern part of that bay. This claim was rejected after arbitration by President MacMahon. His award made in 1875 upheld the border agreed in 1869. A second challenge came from the foundation of a German colony at Angra Pequena, now known as Lüderitz, in Namibia in 1883. Although there was no Portuguese presence there, Portugal had claimed it on the basis of discovery.
During the 1850s, the areas south of Lake Nyasa (now Lake Malawi) and west of the lake were explored by David Livingstone, and several Church of England and Presbyterian missions were established in the Shire Highlands in the 1860s and 1870s. In 1878 the African Lakes Company was established by businessmen with links to the Presbyterian missions. Their aim was to set up a trading company that would work in close co-operation with the missions to combat the slave trade by introducing legitimate trade and to develop European influence in the area. A small mission and trading settlement was established at Blantyre in 1876.