James and Pollard appropriately insist that the articulation of general, "evidence-informed" pedagogical "principles" that can inform teacher judgments and policy-makers rather than detailed instructional "prescriptions" that tell teachers what to do is the most useful way to improve classroom practice at scale. This is surely right: teaching and learning are deeply contextual and highly contingent. Certainly, our experience in Singapore strongly supports this claim, particularly if backed up by appropriately designed "in situ," iterative, authentic and extended professional learning experiences. Moreover, the specific generative principles that James and Pollard identify are substantial and important. However, I am not convinced, given my experience in Singapore and my understanding of research findings more generally, that the principles they isolate are either adequately specified or jointly sufficient to optimise improving the quality of teaching and learning in British schools. But certainly what James and Pollard, and the TLRP team more generally, have achieved makes a unique and significant contribution to that effort and to the broader international movement to design and deliver educational research that is rigorous, relevant and useful. (Contains 1 figure and 1 note.)