Still no confirmation that British merchant ships were warned to stay away from the Black Sea according to a letter of the German naval attaché at Istanbul dated 26 September 1939

In his letter dated Istanbul, Turkey 29 September 1939 No. 61g.Kdos reported the German naval attaché to the Oberkommando der Kriegsmarine at Berlin that the radio messages that the British shipping had to stay away from the Black Sea were still not confirmed. British ships however did not accept cargoes for the Russian Black Sea. Cargoes for Bulgarian and Romanian harbours were still accepted.

Source

Bundesarchiv. German Marineattaché for Turkey, Greece, Romania and Bulgaria 1939-1941. RM 12-II/459.