This article examines how the devolved legislatures of Scotland, Wales and Northern Ireland have developed distinct institutional, normative and conflict-based constitutional identities that position them as constitutional actors within the UK’s territorial order. Moving beyond analyses focused solely on competence allocation and the Sewel Convention, it argues that devolved identity is articulated through institutional design, claims to democratic legitimacy and episodes of contestation with Westminster. Disputes arising from Brexit, the UK Internal Market Act 2020, rights-based legislation and the Northern Ireland Protocol reveal how devolved institutions frame authority in terms of popular sovereignty, civic nationhood, consent and parity of esteem. While parliamentary sovereignty remains legally intact, these developments expose a widening gap between doctrinal hierarchy and constitutional practice. The article contends that the UK now operates as a differentiated constitutional system in which authority is legally centralised yet politically dispersed across multiple constitutional sites.