British open source intelligence (OSINT) and the Holocaust in the Soviet Union: persecution, extermination and partisan warfare

Where does British open source intelligence (OSINT) fit into the intelligence debate surrounding Allied knowledge of the Holocaust? In particular what can this source of intelligence tell us in regards to the opening of the extermination phase of the Holocaust in the Soviet Union? Were the Allies conclusions being falsely influenced by their own OSINT analysts? Or conversely did OSINT provide further evidence (alongside SIGINT decodes) that the Nazis were now committing mass genocide. This article explores these questions by examining the FRPS/FORD OSINT reports from the civilian ruled territories of (and those intended for) the Reichskommissariate Ostland and Ukraine.