A file of miscellaneous Security Service (MI5) correspondence, mostly relating to the circulation of classified documents. The file also includes a detailed report on the ‘Red Orchestra’, a Soviet intelligence network that operated in Western Europe before and during the Second World War. The report outlines the structure of the network, including diagrams of its organisation, lists key members, and summarises its activities and history, from its pre-war origins to the eventual capture and execution of many of the members by the Germans. The file also contains documents discussing the disappearance of an airliner believed to have flown to Yugoslavia, and a request from the Israeli government for the release of a terrorist in prison in Britain.