Alfred Hitchcock's forgotten Holocaust documentary

In 1945, director Alfred Hitchcock, embarked on a difficult film project: Documenting the Nazi atrocities in liberated concentration camps across Europe. It included horrifying scenes from Bergen-Belsen, which was liberated by British troops in April 1945. The film, 'German Concentration Camps Factual Survey,' was to be a lesson for all mankind. The powerful film was lost and forgotten for 70 years.