Simple, separable, unital, monotracial and nuclear C * -algebras are shown to have finite nuclear dimension whenever they absorb the Jiang-Su algebra Z tensorially. This completes the proof of the Toms-Winter conjecture in the unique trace case.The structure theory of simple nuclear C * -algebras is currently undergoing revolutionary progress, driven by the discovery of regularity properties of various flavours: topological, functional analytic and algebraic. Despite the diverse nature of these regularity properties, they are all satisfied by those classes of C * -algebras which have been successfully classified by K -theoretic data, and they all fail spectacularly for the "exotic" algebras in [30,40] which provide counterexamples to Elliott's classification conjecture. The observation that