patrolling a huge area of sea, the British navy found it hard to enforce the treaties as ships from France, Spain, Portugal, and America continued to carry slaves. In 1856, Sultan Majid consolidated his power around the African Great Lakes slave trade. But in 1873, Sir John Kirk informed his successor, Sultan Barghash, that a total blockade of Zanzibar was imminent, and Barghash reluctantly signed the Anglo-Zanzibari treaty which abolished the slave trade in the sultan's territories, closed all slave markets and protected liberated slaves. The relationship between Britain and the German Empire, at that time the nearest relevant colonial power, was formalized by the 1890 Heligoland–Zanzibar Treaty, in which Germany agreed to "recognize the British protectorate over ... the islands of Zanzibar and Pemba". In 1890 Zanzibar became a protectorate (not a colony) of Britain. This status meant it remained under the sovereignty of the Sultan of Zanzibar. Prime Minister Salisbury explained the British position: The condition of a protected dependency is more acceptable to the half civilised races, and more suitable for them than direct dominion. It is cheaper, simpler, less wounding to their self-esteem, gives them more career as public officials, and spares them unnecessary contact with white men. From 1890 to 1913, traditional viziers were in charge; they were supervised by advisors appointed by the Colonial Office. However, in 1913 a switch was made to a system of direct rule through residents (effectively governors) from 1913. The death of the pro-British Sultan Hamad bin Thuwaini on 25 August 1896 and the succession of Sultan Khalid bin Barghash, whom the British did not approve of, led to the Anglo-Zanzibar War. On the morning of 27 August 1896, ships of the Royal Navy destroyed the Beit al Hukum Palace. A cease-fire was declared 38 minutes later, and to this day the bombardment stands as the shortest war in history. Zanzibar became the birthplace of famed British singer-songwriter of Queen, Freddie Mercury. Zanzibar revolution and merger with Tanganyika On 10 December 1963, the Protectorate that had existed over Zanzibar since 1890 was terminated by the United Kingdom. The United Kingdom did not grant Zanzibar independence as such, because the UK had never had sovereignty over Zanzibar. Rather, by the Zanzibar Act 1963 of the United Kingdom, the UK ended the Protectorate and made provision for full self-government in Zanzibar as an independent country within the Commonwealth. Upon the Protectorate