This is the first of a two-part article that presents a new assessment tool - the snapshot - for pre-registration nurses in clinical practice, that is being used at Kingston University/St George's University of London during year 3 of the Diploma and BSc programmes. A pilot study of the use of the snapshot in a simulation environment had previously been undertaken and as a result of this, the snapshot was piloted as part of continuous clinical assessment in practice on two cohorts of third-year pre-registration student nurses. An evaluative study was undertaken. This article describes the background to the project, the literature and the research methods used to undertake the evaluative research study. Part 2 will focus on the findings and a discussion of these findings mapped against the literature.