Immigration and its consequences is one of the most contentious issues in the contemporary world, and historians are engaged in this debate by offering a longer-term perspective. In recent years, research on the United Kingdom's population has placed greater emphasis on population movement in shaping Britain's story, identifying waves of migrants from elsewhere alongside migration within Britain. One neglected aspect of this narrative, however, is the migration of Scots to England, particularly in the age of the regal and parliamentary union, when the changing political relationship between the two kingdoms had an impact on the scale, geographic spread, and opportunities and obstacles of that migration. While a minority of Scottish migrants were unwelcome, or chose to return home, the overwhelming weight of evidence is for those migrants who remained in England. The focus in this article is on that majority group for whom migration was a positive experience, thus raising questions about why these Scots were so successful and why they faced so little native opposition. That process of segmented assimilation offers an insight into the formation of Britain and the shifting ground of national identity associated with the emerging British state. The Scots, moreover, provide a model for “successful” migration, suggesting that a range of factors—principally, an educated, culturally malleable, and economically responsive migrant population, alongside an institutionally and attitudinally flexible host community—need to be in place in order to optimize the chances of migrant assimilation.