Model checking is a formal technique for the automated analysis of system models against formal requirements. Once a suitable model and property have been specified, no further interaction by the analyst is required. However, this does not make the method necessarily user friendly since the checker must be provided with appropriate and complex input data. Furthermore, counter-examples generated by the system are often difficult to interpret. Because of this complexity, model checking is not commonly used, and exhaustive exploration of system models based on finite state descriptions is not exploited within industrial dependable systems design. The paper describes the development of an integrated collection of tools around SMV, intended to make it more accessible to practicing software engineers and in particular those concerned with the human interface issues in complex safety critical systems.