In 1943 , informed by Poles living in London about the massacre in the woods at Katyn of 15,000 Polish servicemen by Britain 's ally , the Soviet Union , Potocki published what he considered to be his most important piece of writing , his '' Katyn Manifesto '' . The British government had been keen to keep the atrocity quiet , which the Soviet Union blamed on Nazi Germany . Potocki was arrested by Special Branch and imprisoned . Later , he was sent to an agricultural camp in Northumberland . This manifesto was the only acknowledgement of the atrocity in English . The full truth of the Katyn massacre was not to emerge for another 50 years . His arrest and conviction was reported as related to the blackout regulations as he was showing a light , and he was reported as saying in court '' Heil Hitler ''
massacre in the woods at Katyn
Katyn massacre
Count Geoffrey Potocki de Montalk