Expertise implies epistemic authority: the expert — by definition — speaks with authority within his or her area of expertise. If the expertise is recognized, the authority automatically follows and doesn’t have to be claimed or argued for.
English says he hopes that this is uncontroversial, but it is not even seriously plausible. Expertise does not imply epistemic authority; it is easy to identify cases where it would be insanely stupid to assume that when expertise is recognized "the authority automatically follows" -- to take just one extremely obvious instance, if the expert were also known to have recently become a pathological liar. Much less obvious cases are also easy to find. This highlights a key distinction between the two concepts that creates an insuperable barrier to accepting this notion that experts "by definition" speak with authority; expertise is had simply by having a relevant kind of dispositional knowledge, whereas epistemic authority is obviously only relevant when there is some kind of actual communication or proposal. So expertise does not imply epistemic authority. It's likewise the case, of course, that epistemic authority does not imply expertise, since recognizing that people can have at least a limited form of epistemic authority in matters on which they are not experts is universal. The two concepts are related, but not rigorously linked together. It is an error to slide from one to the other without regard for the conditions of the case in question.