Extreme forms of custody represent the boundary-points of state power. The configuration of the most restrictive corners of prison systems, and what goes on within them, is highly instructive in exposing the objectives, limits and implications of state coercion at its most severe. Based on data collected in England & Wales and Norway, this article has two main aims. The first is to explore the degree to which ‘deep-end’ confinement differs between jurisdictions with quite different penal philosophies. The second is to understand how the most extreme form of confinement in each jurisdiction differs from the more typical carceral experiences within each system and its overall penal ethos. Empirically, then, the article seeks to shine light into the deepest dominions of both prison systems, illuminating the experiential texture of extreme forms of imprisonment. It concludes by asking what can be inferred about Nordic exceptionalism, and about deep-end confinement more generally, through analysing these domains.