This journal strongly supports the sharing of data to support research and quality improvement. However, this needs to be done in a way that ensures the benefits vastly outweigh the risks, and vitally using methods which are inspire both public and professional confidences--robust pseudonymisation is needed to achieve this. The case for using routine data for research has already been well made and probably also for quality improvement; however, clearer mechanisms are needed of how we test that the public interest is served. Ensuring that the public interest is served is essential if we are to maintain patients' and public's trust, especially in the English National Health Service where the realpolitik is that patients can opt out of data sharing.