The idea for this paper came from a debate at the 1998 ISCRAT conference in Denmark on cultural-historical activity theory (CHAT). A leading activist in the movement to bring CHAT into systems design, Bonnie Nardi, asked the question; would design not benefit more from training better ethnographers than from burdening them with such a complex set of theoretical concepts and debates as CHAT? This paper seeks to answer that question on the basis of our experiences applying CHAT concepts in a long-term design ethnography at a UK newspaper. It examines the history of the often controversial triadic relationship between ethnography, theory and systems design and argues that the CHAT framework provided us with the opportunity to move from ethnographic intuition to design insight, and that therefore the answer to Nardi's question is no - simply training good ethnographers is unlikely to be enough for a number of reasons (not least of which is the problem of how inexperienced fieldworkers become design ethnographers). The explicit use of theoretical frameworks, at least those such as CHAT which are particularly suited to design issues, discourages the tendency for ethnographers to see themselves as 'proxy users' by encouraging greater reflexivity about the researcher's role in constructing the object of study. At a more pragmatic level, it helps the fieldworker navigate the apparently never-ending mass of 'potentially interesting material' any field experience throws up.