The Unfederated Malay States, on the other hand, maintained their quasi-independence, had more autonomy, and instead of having a Resident they were required only to accept a British Advisor, though in reality they were still bound by treaty to accept the advice. The British undertook far less economic exploitation as they primarily wished to just keep these states in line. Indeed, limited economic potential in these states saved the UFMS from further British political meddling. Perlis, Kedah, Kelantan and Terengganu were surrendered by Siam after the Anglo-Siamese Treaty of 1909. Independent Johor, meanwhile, had to surrender Singapore to the British earlier on. Despite the Sultan's political effort, he was forced to accept an advisor in 1914, becoming the last Malay state to lose its sovereignty (British involvement in Johor actually began as early as 1885).