For many people, discussion of language and identity at national borders will first bring to mind contexts in which different languages - perhaps mutually unintelligible or unrelated ones - are spoken on either side of an international frontier, across which the movement of people, goods and services, and even ideas, is controlled. Examples of such boundaries are plentiful, and some of them are described in other chapters in this book. However, there are also cases in which borders between nations are uncontrolled, and where the linguistic varieties spoken on either side of the border are dialects of one language. Several such contexts are also examined in this volume (see the chapters by Boberg, Coupland, Kallen, Redinger and Llamas, and Montgomery). In contexts of this second type, the role played by language behaviour in how social groups self-identify and how they are identified by others, and the significance of the border in these identity-construction processes, are factors that deserve every bit as much attention from researchers as do situations of the first kind. Indeed, in regions where trans-border movement is uncontrolled and where a language is shared by populations living on either side of the border, the dependencies between subtle accent/dialect differences and speakers' identities may become particularly meaningful and finely balanced. The border between Scotland and England is one such region.