Prior to the recognition of Spanish presence in the Philippine archipelago, a protocol known as the Madrid Protocol of 1885 was signed between the governments of the United Kingdom, Germany and Spain in Madrid to cement Spanish influence and recognise their sovereignty over the Sultanate of Sulu—in return for Spain's relinquishing its claim to the former possessions of the Sultanate in northern Borneo. The British administration then established the first railway network in northern Borneo, known as the North Borneo Railway. During this time, the British sponsored a large number of Chinese workers to migrate to northern Borneo to work in European plantation and mines, and the Dutch followed suit to increase their economic production. By 1888, North Borneo, Sarawak and Brunei in northern Borneo had become British protectorate. The area in southern Borneo was made Dutch protectorate in 1891. The Dutch who already claimed the whole Borneo were asked by Britain to delimit their boundaries between the two colonial territories to avoid further conflicts. The British and Dutch governments had signed the Anglo-Dutch Treaty of 1824 to exchange trading ports in Malay Peninsula and Sumatra that were under their controls and assert spheres of influence. This resulted in indirectly establishing British- and Dutch-controlled areas in the north (Malay Peninsula) and south (Sumatra and Riau Islands) respectively.