The Royal College of Paediatrics and Child Health (RCPCH) incepted a new end-of-training assessment in 2012, known as START, the Speciality Trainee Assessment of Readiness for Tenure [as a Consultant]. It is a novel, formative, multi-scenario, OSCE-style, out-of-workplace assessment using unseen scenarios with generic, external assessors undertaken in the trainees’ penultimate training year. This study considers whether this assessment assists in preparing senior paediatric trainees for consultant working. A mixed qualitative and quantitative study in the post-positivist paradigm was designed. Subjects were paediatricians who have taken START and completed their paediatric training. Methods were an on-line questionnaire survey and a key informant interview. The assessment is viewed positively, but some trainees report negative experiences. They find value in the formative feedback which generally helps direct trainees towards focussing their training in their final year before ending their training and consultant appointment. For many respondents, the assessment highlighted areas for further development, was relevant for consultant working and useful for consultant interview preparation. Of least value was travelling, cost, assessor performance, feedback quality, feeling like a summative exam and sub-speciality involvement. Many respondents felt the assessment highlighted areas to develop in their subsequent training. Overall START supports transition to consultant working.