In this paper I reflect on three years interviewing on the British Library's An Oral History Of British Science. I explore how we turned our strategic hopes for the project, as a cross section of past scientific activity in Britain told through the voices of those involved, into a reality, by discussing practical fieldwork experiences of interviewing scientists and engineers. An oral history project of this nature creates sources for historians, but also individual histories, each with its own story to tell and impressions of the past that differ from the considered accounts of historians far removed from events. I discuss questioning and navigating the differences in mindset between historian and scientist, and how this conditions the interview and creates a dual authored document: the memories of the individual scientist or engineer shaped through conversation with a historian, creating a blend of science, history of science, and life story oral history. I consider some of the challenges of conducting oral life histories focused on the individual, with people who spent their lives caught up in teamwork environments and large, complex technical systems with life stories of their own. Finally I consider what such material, both individual interviews and collectively, adds to our understanding of the history of science in Britain and its practitioners.