At a time when George Gallup described public opinion polls as “just out of their swaddling clothes”, Geoffrey Pyke’s 1939 attempt to gauge what ordinary Germans thought about the Nazis – and the prospect of war with Britain, France and Russia – was unprecedented. Without the support or backing of officials in Whitehall, Pyke concocted an ambitious yet breathtakingly simple scheme to dissuade Germany’s leaders that they lacked the popular support required for war. Pyke set out to recruit German-speaking ‘conversationalists’ who would be willing to visit Germany and record the views of ordinary Germans whilst posing as tourists. Paying close attention to the technical innovations pioneered by Gallup’s American Institute of Public Opinion, Pyke carefully crafted the wording and sequence of the questions his pollsters would ask; and gave considerable thought to the range of respondents required to ensure their views would accurately reflect those of the population as a whole. Recognising that evidencing his survey’s validity would be critical to its utility in the subsequent influence operations he had in mind, Pyke even arranged for five of his ‘conversationalists’ to operate independently in the same city for several days (and unbeknownst to one another) to demonstrate the consistency of their findings. Meanwhile, the suitability of potential pollsters was rigorously assessed by a recent German refugee (Rolfe Rünkel) – who ensured that successful applicants could accurately recall not only the questions (which they were required to slip into the conversations they struck up with ordinary Germans), but also the answers to these questions (which could only to be written down afterwards, and in private). Instructed by Pyke to conform to the popular and affectionate German caricature of the eccentric and comfort-obsessed English tourist abroad, Pyke’s amateur pollsters had an unforeseen advantage over their professional counterparts. The necessity of concealing their true identities and intentions gave them licence to contrive a level of rapport that substantially attenuated any recourse to response bias or the vagaries of self-censorship. Indeed, when sharing their views and opinions with these amiable foreigners, it is clear that Pyke’s instructions had a disarming effect on a good many of the Germans they approached – making them much more willing to share what they actually thought. Although Pyke’s 10 amateur pollsters managed to complete 232 interviews in 14 cities during their first 2 weeks in Germany, the success of the scheme was overtaken by events when – on 21^st August 1939 – they witnessed first-hand the dramatic shift in public opinion that took place when news leaked of the impending Molotov-Ribbentrop Pact. Forced to abandon any further survey work, they were lucky to escape home before the outbreak of war 10 days later. Drawing on the detailed accounts provided by David Lampe (1959) and Henry Hemming (2014) – and on archive material held by the University of Cambridge – this presentation assesses the success of Pyke’s unique experiment in covert sentiment analysis and what this might tell us about: the prospects for peace in 1939; and how we might strengthen contemporary approaches to influence operations.