This paper introduces a Relational Affective Formulation of severe narcissistic and borderline disorders. The formulation is grounded in psychoanalytic and neuroscientific theory, clinical observation and therapeutic work with hospitalised patients. It provides a conceptual framework for psychodynamic psychiatrists, therapists and psychosocial practitioners working in teams. Paying particular attention to the central place of affect, projective and introjective processes, claustro-agoraphobic phenomena, regression and the place of both deficits and dynamic defences in the failure of symbolisation, the case is made that this framework is suited to therapeutic work with patients who are highly suicidal and complex. The application of this formulation to service design and treatment pathways is described along with a summary of the body of psychoanalytic thinking which contributed to its development. The formulation is the cornerstone of a practice guide currently under development.