Drawing upon recently published research and previously unseen archival sources, the article provides a new explanation of the British conquest of Burma in 1885. Previous explanations have attributed British motives for conquest to either the need to defend the eastern borders of Britain's Indian empire from French expansion in mainland south-east Asia, or the desire to open Burma and China to British trade and investment at a time of perceived economic depression. The article contends that while French expansionism certainly loomed large in the British decision to invade, commercial interests and considerations were pivotal in persuading the British government of the French threat. In particular, the role of London-based ‘gentlemanly capitalists’ in shaping government policy is emphasized and explored. In the process, new insights into the methods and strategies of City financiers are revealed. Besides contributing to the debate surrounding the ‘gentlemanly capitalism’ thesis of Cain and Hopkins, the article also evaluates the importance of socio-economic conditions in Burma itself as a factor which stimulated British expansion.