In World War II Nigel de Grey was assigned to the "Government Code and Cypher School" (GC&amp;CS) at Bletchley Park, where he concentrated on German traffic encrypted on the Enigma cipher machine. In September 1941 he provided a report to the Prime Minister with the first references from German authorities to their own police battalions systematically levelling villages and removing their populations. One signal boasted of 30,000 executions "in the central area". Following a warning made in a speech to parliament by Churchill, a German circular in October 1941 cautioned that no further references to "sensitive operations" should be made on wireless channels.