Since the EIC's establishment of early British presence in Penang, the British had maintained another trading post in Singapore, avoiding involvement in the affairs of the nearby Malay sultanate states. In 1822, the British authority in India sent British diplomat John Crawfurd to Siam to negotiate trade concessions and gather information with a view to restoring the Sultan of Kedah to the throne. The mission failed. In 1823, the Sultanates of Perak and Selangor signed a joint agreement to block the Dutch tin monopoly in their territories. EIC policy shifted with the First Anglo-Burmese War in 1824, Siam then becoming an important ally.