OpenPrescribing is our most widely used applied data science project, with over 130,000 unique users a year. It lets any interested user explore NHS GP prescribing behaviour across the whole country, down to the level of individual doses and brands, of individual drugs, at individual practices, each month. We have a range of prespecified measures showing opportunities to improve the quality, safety, and cost effectiveness of prescribing. We also let users devise their own analyses and alerts. OpenPrescribing represents a huge amount of complex data science “under the bonnet”, with papers on our innovative methods published in BMJ and elsewhere. We have also generated a large body of research on trends and variation in clinicians' choice of treatments, and what drives change in clinical practice, including randomised trials on our own interventions. Alongside this we have generated extensive technical and policy insights on how data can be put to good use in the NHS, where the blockers lie, and how they can be overcome.