In Latin America, where British imperial expansion had left little administrative trace, Argentina was nonetheless profoundly affected by British investment and imported British technical expertise. Among the more modest examples of British expansionism in Argentina was the arrival, from 1865 onwards, of Welsh immigrants eager to establish a colony in Patagonia isolated from the seemingly unstoppable progress of Anglicisation by an overwhelmingly hegemonic Victorian England. By the time of the First World War, however, the Celtic character of the colony could no longer be taken for granted: Argentine government pressures had already meant that the Welsh-speaking colony was now more firmly integrated into the nation-building process. Friction which then developed between the Welsh community and the Argentine government acted as one of the push factors which sent Welsh Patagonians back to Wales and on to Australia, for example…To this process of integration the Great War added new pressures in the form of the question of loyalty to Britain during the conflict. Those who stayed in Patagonia during the war often expressed views which were pro-British and the Argentine province became a source of recruitment for the British armed services…Using a range of sources, this paper attempts to show that the Welshness of the Patagonian colonists had not destroyed their British patriotism: the latter survived and even came to the fore during the conflict of 1914-18.