Dr Paul McCrory is a world-renowned concussion expert whose work shaped concussion policy across global sport for the past 20 years. In his work, and through his role on the influential Concussion in Sport Group, McCrory had previously adopted a sceptical view on the link between concussions and chronic traumatic encephalopathy (CTE) – a progressive brain condition whose symptoms are similar to Alzheimer’s disease. Last week, the British Journal of Sports Medicine (BJSM) retracted nine of his articles and attached an ‘expression of concern’ to another 74. In an editorial, the BJSM, and its publisher, BMJ, stated that ‘their trust in McCrory’s work –specifically the articles that he has published as a single author – is broken’. Ian Sample speaks to senior sports writer Andy Bull about how the scandal unfolded, what it could mean for players and what is likely to happen next. Help support our independent journalism at theguardian.com/sciencepod