In an environment in which most regulatory and authoritative health strategy decisions are made on the basis of randomised control trials, real-world evidence (RWE), primarily derived from electronic health records, remains a second-class citizen. Real world evidence is widely taken to include Pragmatic clinical trials and insights derived from the distributed analysis of large volumes of routinely collected health data and registry data (so called big data). This presentation will look at the growing scale and reputation of big health data, the ways in which good governance principles and better quality data are creating reusable data at scale, how platforms and tools are enabling better quality evidence generation, and the perspectives of different stakeholders towards the positioning of RWE in decision making: by regulators, health technology assessment agencies, outcomes benchmarking and value based care. This talk will review how we are presently able to generate trustworthy real world evidence, what we mean by that, and the barriers that remain to trusting it. These remaining barriers will need to be tackled by future health informatics research.