The United Kingdom continues to undergo a rapid process of constitutional change, with an ongoing redistribution of law-making and governmental powers to different parts of the Union under an expanded rubric of ‘devolution'. This article illuminates a pervasive sense of territorial constitutional crisis and opportunity in the most recent period, familiarly associated with, but not confined to, Scotland. Constructive and flexible federal-type responses inside a famously uncodified constitution are championed. Wales, commonly treated as a junior partner in the United Kingdom, presents special challenges for constitutional and legal analysis and distinctive perspectives on the Union which have not received the attention they deserve. In tackling this deficiency, the article elaborates a ‘new Union’ concept of a looser and less hierarchical set of constitutional arrangements in which several systems of parliamentary government are grounded in popular sovereignty and cooperate for mutual benefit.