There was a serious touch with British colonial interests when Siam conquered the Sultanate Kedah on the Malay Peninsula in 1821. Kedah belonged to the sphere of interest of Great Britain. In the following year, Siam had to recognise the pre-conquest status after tough negotiations with the British envoy John Crawfurd. There was also the cautious resumption of trade and missionary activity in this epoch. In particular, British traders such as Robert Hunter ("discoverer" of the conjoined brothers Chang and Eng, the original "Siamese twins") or James Hayes, but also missionaries from Europe and the United States like Jacob Tomlin, Karl Gützlaff, Dan Beach Bradley and Jean-Baptiste Pallegoix became active in Siam. In 1825 an agreement was signed with British emissary Henry Burney; Siam recognised British colonial possessions on the Malay Peninsula and made commercial concessions. This agreement was due not least to the rapid British success in the First Anglo-Burmese War.