Interview with John Ellis, Clerk Maxwell Professor of Theoretical Physics at King’s College London, and Visiting Scientist at CERN. Ellis discusses the g-2 experiment at Fermilab and where he sees current efforts geared toward understanding physics within the Standard Model, and pursuing new physics beyond it. He recounts his childhood in a small town north of London and his innate interest in physics before he understood that it was a proper field of study. Ellis discusses his education at Cambridge and the department’s strength in particle physics, general relativity, and cosmology, and he explains the relevance of the deep inelastic scattering research at SLAC for his thesis on approximate symmetries of hadrons. He describes the intellectual influence of Bruno Zumino and his decision to go to SLAC for his postdoctoral research to work on scale invariance. Ellis discusses his subsequent research at Caltech and he explains why he would have appreciated more the significance of asymptotic freedom had he better understood field theory at that point. He discusses his subsequent position at CERN and is collaboration with Mary Gaillard on semileptonic decays of charm. Ellis narrates the famous “penguin diagram” that he developed with Melissa Franklin and his interest in grand unification and how it differs from the so-called “theory of everything.” He describes the optimism in the 1980s that supersymmetry would be found and its possible utility in the search for dark matter. Ellis discusses his involvement with LEP and axion physics, and he reflects on the spirit of competition and collaboration between ATLAS and CMS in the run up to the Higgs discovery. He explains the new questions that became feasible as a result of the discovery and his interests in both gravitational waves and supernovae. Ellis describes the AION experiment, the important physics research currently in the works in China, and key recent developments in quantum gravity. At the end of the interview, Ellis conveys his belief in the importance of science communication, he minimizes the importance of the h-index as a measure of excellence, and in reflecting on his own career, he cautions against younger physicists becoming overly-specialized.