The British introduced several changes to the local political structure, exerting influence on the appointment of the Sultan and restricting the power of his chiefs to Malay local matters. The Sultan and his chiefs were no longer entitled to collect taxes, but received a monthly allowance from the state treasury in compensation. British intervention marked the beginning of Perak's transition from a primarily Malay society to a multi-ethnic population. The new style of government worked to promote a market-driven economy, maintain law and order, and combat slavery, seen by the British as an obstacle to economic development and incompatible with a capitalist economy. Under the Anglo-Siamese Treaty, signed in Bangkok in 1909, Siam ceded to Great Britain its northern Malay tributary states of Kedah, Kelantan, Perlis, and Terengganu and nearby islands. Exceptions were the Patani region, which remained under Siamese rule, and Perak, which regained the previously lost inland territory that became the Hulu Perak District. The treaty terms stipulated that the British, through their government of the FMS, would assume responsibility for all debts owed to Siam by the four ceded Malay states, and relinquish British extraterritorial rights in Siam.