British tanker Helka visited the Black Sea according to a letter of the German naval attaché at Istanbul dated3 February 1940

In his letter dated Istanbul, Turkey 3 February 1940 No. 712 g. reported the German naval attaché to the Oberkommando der Wehrmacht Abteilung Ausland the neutral ships passing Istanbul coming out of the Black Sea and loaded with contraband for or chartered by the enemy. An item reported the British tanker Helka on 29 January with 4,500 ton petrol from Constanta, Romania towards Algiers. Unarmed.

Source

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