This collection brings together in one volume the principal essays of David Sellar (1941-2019) on Scottish legal history, focused upon the influence of Celtic, Canon, English and customary law in the development of Scots law. It includes a paper written during Sellar's time as Lord Lyon King of Arms (2008-2014) but left unpublished at his death, along with a general introduction by Hector L. MacQueen.Sellar was a pioneering historian of Scots law who rejected previous interpretations of the subject as a series of false starts and rejected experiments. He emphasised instead the continuity of legal development, with change a process of integration of external influences from very early times on. Sellar's approach, articulated mainly through essays published in diverse places over four decades, has had significant influence upon our general understanding of legal history in Scotland as well as leading to appreciation elsewhere of its comparative significance. By gathering the major essays in a single collection, this book demonstrates the scope and reach of Sellar's overall contribution. It provides an opportunity to view Sellar's work as a whole and to access his distinctive perspective on the overall trajectory of Scottish law.