By the mid-19th century British traders had created a profitable market for opium in China. The Chinese government tried to ban the import of opium, as it had led to widespread addiction among the Chinese population. The British Empire retaliated with armed force resulting in the two 'Opium Wars' (1839-1860). The British forced the Chinese to accept their conditions and created the largest and most lucrative drugs cartel in the world. However, all the wealth built up by the British Empire was spent by 1918 fighting another conflict, the First World War.The opium trade also left its mark in Wales. John Rees (1801-1855), a ship's captain of Tenby, made the first accurate charts of the Chinese coast which were used in the First Opium War. Rees made his fortune trading opium in China, investing the money in property in Pembrokeshire. Numbers 1-5 of Lexden Terrace, one of the finest of the Tenby terraces, were built for him.