EDITOR—I strongly oppose the proposition of Potts et al.1 For all the difficulties of doing high quality randomised controlled trials of some research questions, or in challenging settings, making arbitrary decisions about the “obviousness” of the effectiveness of interventions based on observational evidence cannot be the way forward. This point is well made by the readers with expert knowledge who have already responded about the specific examples described by Potts et al.2

Other readers have criticised the naïveté of the argument but seem to accept the underlying sentiment that the world should not always wait for evidence from randomised controlled trials. This point of …