The British establishment of Singapore on the Malay Peninsula in 1819 by Sir Stamford Raffles exacerbated the tension between the two nations, especially as the Dutch claimed that the treaty signed between Raffles and the Sultan of Johor was invalid and that the Sultanate of Johor was under the Dutch sphere of influence. The questions surrounding the fate of Dutch trading rights in British India and the formerly Dutch possessions in the area also became a point of contention between Calcutta and Batavia. In 1820, under pressures from British merchants with interests in the Far East, negotiations to clarify the situation in Southeast Asia started.