For the past 17 years I have visited ECMWF annually to work on the evaluation of the model physics using observational data, especially data from field programs. It has been a time of rapid model development. Tony was an early enthusiastic supporter of this work. He would say: “The more errors you find, the more we can fix”. He understood the science, and he had an excellent understanding of science management. I will outline some of the highlights and progress made in identifying systematic errors and improving model physics parameterizations; and discuss where we stand now.