On the outbreak of war, men from the Dominions were scattered across the British Empire. As each Dominion began recruiting their expeditionary forces at home, the issue arose whether these expatriates, especially those resident in the United Kingdom, should join the British Army or be able to enlist in their Dominion's force. Canada and New Zealand allowed recruiting for the CEF and NZEF in the UK. Many Anglophone White South Africans joined a “colonial” battalion of the Royal Fusiliers. The Australian Government refused to allow Australians in the UK to join the AIF, despite the repeated requests of the Australian expatriate community. This paper examines the questions of British and sub-Imperial Dominion identities as well as the practical policy considerations raised by this issue. It argues that there is some evidence of nascent Dominion nationalism—the Canadian High Commission in London issued what became known as “a Certificate of Canadian Citizenship” to expatriates— but that Dominion Governments generally based their decisions on this issue based on cost and domestic political considerations.