Brooke originally planned to sail to Marudu Bay in northwestern Borneo, but the British Governor-General in Singapore asked him to thank Raja Muda Hashim in southwestern Borneo. The following month he sailed to the western coast of the island and on 14 August 1839, berthed his schooner on the banks of the Sarawak River and met Hashim to deliver the message. The Raja told Brooke that his presence in the area was to control a rebellion against the Sultanate of Brunei caused by the oppressive policies of Pengiran Indera Mahkota, a kinsman of the Sultan. Mahkota had earlier been dispatched by the Sultan to monopolise the antimony in the area; which as a result directly affecting the incomes of the local Malays there and growing frustration from the indigenous Land Dayak who had been forced to work in the mines for about 10 years. It has also been alleged that the rebellion against Brunei was aided by the neighbouring Sultanate of Sambas and the government of the Dutch East Indies, who wanted to establish economic rights over the antimony. Despite Hashim's efforts to stop the rebellion, it came to no avail thus leading him to seek direct help from Brooke.