The Dutch began to intervene in the southern part of the island upon resuming contact in 1815, posting Residents to Banjarmasin, Pontianak and Sambas and Assistant-Residents to Landak and Mampawa. The Sultanate of Brunei in 1842 granted large parts of land in Sarawak to the English adventurer James Brooke, as a reward for his help in quelling a local rebellion. Brooke established the Raj of Sarawak and was recognised as its rajah after paying a fee to the Sultanate. He established a monarchy, and the Brooke dynasty (through his nephew and great-nephew) ruled Sarawak for 100 years; the leaders were known as the White Rajahs. Brooke also acquired the island of Labuan for Great Britain in 1846 through the Treaty of Labuan with the Sultan of Brunei, Omar Ali Saifuddin II on 18 December 1846. The region of northern Borneo came under the administration of North Borneo Chartered Company following the acquisition of territory from the Sultanates of Brunei and Sulu by a German businessman and adventurer named Baron von Overbeck, before it was passed to British Dent brothers (comprising Alfred Dent and Edward Dent). Further expansion by the British continued into the Borneo interior. This led the 26th Sultan of Brunei, Hashim Jalilul Alam Aqamaddin to appeal the British to halt such efforts, and as a result a Treaty of Protection was signed in 1888, rendering Brunei a British protectorate.