Our understanding and use of simulation based training has evolved from simply practicing or learning performance in an accurate re-creation of the operating room as first envisaged by anaesthetist simulation pioneers. The efficacy of simulation training has been quantitatively demonstrated in prospective, randomized, double blinded studies. Simulation training models used in these studies have varied from bespoke models for training intra-corporeal suturing skills, VR emulation models for basic laparoscopic skill acquisition through to full physics VR simulations for the learning of endovascular skills. The understanding of why specific simulation models are effective needs to be better understood by trainers, researchers and engineers if simulation based training is to deliver on its potential for more advanced skills training but more importantly for the acquisition of procedural wisdom. This development will require a better understanding and more forthright approach to the issue of simulation fidelity.