What emerges from the three cases is that interrogation was a central component of the wartime state, and that it remained essential immediately after the war. It also delivered: each camp extracted the information it was tasked to obtain, and its output was generally considered reliable. At the same time, there were biases that ran so deep that they were not recognised, with the three cases confirming Britain’s failure to grasp the extent and nature of mass murder and genocide, even as told by its own sources. The comparison also shows that interrogation relied on forms of psychological manipulation, though the character and intensity of those methods differed between the different camps. At the same time, higher command had an interest in ensuring that all detainees were treated in a manner consistent with Britain’s self-image and legal obligations. While abusive practices did occur, they affected a relatively small number of those under interrogation and were out of sync with standard practices. Taken together, these findings confirm that interrogation was not an isolated activity but one shaped by wider institutional priorities and cultural attitudes.

Interrogating Nazism uncovers a history in which interrogation became a valuable information-gathering method in the context of the Second World War, giving Britain remarkable knowledge of Nazi Germany in the process. Much of that knowledge, concerning individuals, armies, atrocities and numerous other subjects, could not have been gained through any other means in such detail. Not only was it obtained in interrogation camps, it was also preserved in tens of thousands of reports, indexes and verbatim transcripts of secretly recorded discussions. In many ways, the sources emanating from interrogation are a ‘first oral history’ of the Second World War. This is a term that David Cesarani used to describe the interviews of Allied psychologists with German soldiers – some of which had their origins in the interrogation camps studied here – but which is appropriate for much of the archival material that makes up this book.