A file of reports and memoranda produced by the Security Service (MI5) discussing the arrest of the Free French Admiral Muselier after allegations of treason. The documents include reports outlining the details of the case and Muselier’s arrest and subsequent treatment; an account of the process by which documents were forged to initiate the case; complaints about the treatment of Muselier by the French, and the potential effects this might have; a report of the arrest of the French wife of a Brazilian diplomatic official, who was suspected of assisting in the passing of information to the Axis; a letter in French from Charles de Gaulle on the case; and arrangements for postal censorship of the Brazilian embassy in London.