This paper examines the words and deeds of the British merchant banker Charles Addis through the lens provided by Transnational Capitalist Class (TCC) theory. Addis was a leading figure in the Hongkong and Shanghai Banking Corporation (HSBC), which was and is an important multinational. In the early twentieth century, he promoted the ethos of commercial cosmopolitanism, a mental framework in which national loyalties are subordinated to other abstract principles, such as a code of commercial honour, loyalty to business partners irrespective of nationality, and the teachings of classical liberalism. Commercial cosmopolitanism was the hegemonic ideology in Britain during Addis’s youth, but it became increasingly unpopular before and especially during the First World War. A committed classical liberal, Addis articulated the ideology of commercial cosmopolitanism in his diary, private correspondence, and many public statements. The paper links Addis’s ideology to the strategy of the HSBC and shows how the firm sought to continue trading with German firms in China as far as British law and public opinion would permit. The paper shows that Addis sought to reduce the impact of the war on the business operations of HSBC and the overall international economy. Addis’s ideas about wartime developments in British and German financial services, particularly the bank merger wave experienced by both countries, are also explored, as are his prophetic comments about the Too Big To Fail problem in banking. The paper also examines Addis’s role in the British deliberations that proceeded the Versailles conference of 1919. The paper observes that Addis was allied with John Maynard Keynes, another prominent opponent of the Versailles peace settlement.