Why has so little evidence of the efficacy of accreditation programmes been published in the peer-reviewed literature? Since its introduction in the 1970s accreditation has spread across the world to become an established part of healthcare systems in over 70 countries and there is an associated international body.1 It is a textbook case of Everett Rogers’ Diffusion of innovation, whereby an idea whose time has come is adopted first by early proponents, then is received by the majority, and then becomes normal practice.2 However, the empirical evidence base for accreditation programmes is substantially undeveloped. It is not as if the challenge to publish evidence has been missing. There have been many calls in the international literature for research into accreditation.3^–6 So while it is accepted that accreditation programmes have been an important driver to improve quality and safety in healthcare organisations, …