In the mid-19th century the British tolerated the independent Boer republics by agreeing to a boundary between the Natal colony and Zululand. However, the discovery of diamonds at Kimberley in 1867 changed their policy. First, they annexed West Griqualand where the diamond mines were located, then proposed the Boer republics join with them in a Confederation. When this proposal was rejected, the British annexed Transvaal and consequently inherited a festering border dispute between the Boers and the Zulu. The new British High Commissioner, Sir Henry Bartle Frere, arrived in 1877 with a mandate to retry implementing the Confederation. Meanwhile, the Zulu determination to protect their territorial integrity was inimical to British interests. Accordingly, in December 1878, he issued the Zulu king Ceteshwayo with an ultimatum demanding, amongst other conditions, the disbanding of their army, and their acceptance of British annexation. The scene was set for armed confrontation.