This article discusses the rationale behind British intervention in the Taiping civil war in China and the episode’s wider significance for understanding nineteenth-century British imperial expansion. I argue that the most productive way to understand the shape of the limited British intervention in the war is through analysing the relative strength of distinct bridgeheads of British interest in China. British interests in Shanghai grew rapidly in the Taiping period and helped to draw in intervention against the Taiping armies when they attacked the port in 1860 and 1862. The strict limitation of this intervention, which did not result in any imperial expansion in China, was a result of the consistent underperformance of the wider British trade with China. Without a growth in this trade, the expense of an extensive intervention and its potential consequences could not be justified. The episode suggests that analyses of local conditions and the strength of local ties to metropolitan resources are important for understanding the wider pattern of British imperial expansion.