British Security Service files from Gale’s Political Extremism and Radicalism archive have a huge amount to tell us about British political life in the twentieth century. These files deal with the activities of extreme British political figures and movements. At first, these files may seem somewhat complex, compiled in large folders, containing information which spans long periods of time and refers to a range of different figures, often with little context. However, once you get an understanding of how the archival documents are best used and approached, there are huge benefits to using them for academic research.