its Commissioner, Harry Johnson, refused to act as a BSAC appointee, in particular on Rhodes' demand that all Crown lands in the protectorate should be transferred to BSAC control and that Johnson should also facilitate the transfer of African lands to it Dispute with Portugal At the start of the 19th century, effective Portuguese government in Mozambique was limited to the ports of Mozambique Island, Ibo, Quelimane, Sofala, Inhambane and Lourenço Marques and the outposts at Sena and Tete in the Zambezi valley. Although Portugal claimed sovereignty over Angoche and a number of smaller Muslim coastal towns, these were virtually independent. In the Zambezi valley, Portugal had also initiated the Prazo system of large leased estates under nominal Portuguese rule. By the end of the 18th century, this area in the valleys of the Zambezi and lower Shire River were controlled by a few families that claimed to be Portuguese subjects but which were virtually independent. In the interior of what is today southern and central Mozambique, there was not even a pretence of Portuguese control. The nadir of Portuguese fortunes was reached in the 1830s and 1840s when Lourenço Marques was sacked in 1833 and Sofala in 1835; Zumbo was abandoned in 1836; Afro-Portuguese settlers near Vila de Sena were forced to pay tribute to the Gaza Empire and Angoche fought off a Portuguese attempt to prevent it from slave-trading in 1847. However, around 1840 the Portuguese government embarked on a series of military campaigns to bring the prazos and the Muslim coastal towns under its effective control. The General Act of the Berlin Conference dated 26 February 1885, which introduced the principle of effective occupation was potentially damaging to Portuguese claims in Mozambique. Article 34 required a power acquiring land on the coasts of Africa outside of its previous possessions to notify the other signatories of the Act so they could protest against such claims. Article 35 of the Act provided that rights could only be acquired over previously uncolonised lands if the power claiming them had established sufficient authority there to protect existing rights and the freedom of trade. This normally implied making treaties with local rulers, establishing an administration and exercising police powers. Initially, Portugal claimed that the Berlin Treaty did not apply, and it was not required to issue notifications or establish effective occupation, as Portugal's claim to the Mozambique coast had existed for centuries