This article examines the British humanitarian relief campaign initiated by the Committee for Relieving the Distresses in Germany and Other Parts of the Continent (1805–1815). It demonstrates the significance of two aspects for the campaign: the activism of London-based immigrant communities on the one hand, and British solidarity with allied countries during the Napoleonic Wars and the related matter of national mobilisation against France on the other. While immigrant activism was a major driving force of the campaign, its impact depended on the integration of immigrants into British society and on the mobilisation of Britons. Moreover, while the alliance with German states was often underlined in the publicity efforts of the campaign, wider humanitarian concerns were also addressed.