Characterising circulatory dysfunction and choosing a suitable treatment is often difficult and time consuming. This paper outlines a numerically stable minimal model of the human cardiovascular system (CVS) specifically aimed for rapid, on-site modelling to assist in diagnosis and treatment. A minimal number of governing equations and a realistic valve law are used to accurately capture trends in CVS dynamics. The model is shown to have long-term stability and consistency with non-specific initial conditions. Examples of model verification are shown for experimentally measured static and transient response data. The model is also verified to capture commonly seen changes in CVS function as a result of disease. These examples illustrate the power of the minimal model for capturing CVS dynamics in health and disease, while its simplicity enables its use as a clinical aid.