Radiotherapy is a major treatment option in the management of many types of cancer. It's one of the safest of treatments, saving, prolonging, and improving the quality of lives for millions of people around the world each year (Eaton et al. 2018; WHO 2008). Although our treatments have become more complex and more efficacious, there is still the risk of harm, personal tragedy, or even fatal injury to a very small percentage of patients (RCR 2008b; WHO 2008). There is a continual drive to reduce this risk, not just by the improvement of procedures and processes and by the use of more technology, but also by learning from mistakes and errors made and those that have nearly amounted to larger mistakes but were stopped beforehand (near misses). For this to be effective, it requires an open and honest no-blame reporting and review structure to be in place in radiotherapy departments around the world, feeding information through at local, national, and international levels (Pawlicki et al. 2017; RCR 2008b; Eaton et al. 2018; Findlay et al. 2016; Milosevic et al. 2016; Chang et al. 2014; IAEA 2016a; IAEA 2018; Ford and Evans 2018).