By the time of King Mongkut's reign (Rama IV, 1851–1868), the city had outgrown its original defensive walls, and the King ordered the digging of Khlong Phadung Krung Kasem to serve as a new outer moat surrounding the city proper. The canal separated Bang Rak, on the far side from the city, from the Chinatown area, and as the country began modernizing and opened to the West under Mongkut's reign, European visitors began establishing themselves here. The Bowring Treaty was signed with the British in 1855, liberalizing trade and granting diplomatic concessions, and other Western countries followed suit. Consulates, trading companies and expatriate communities were established in the waterfront area, which became the city's European quarter.