[2] On returning to Alexandria, Osiris received a package from the commanding officer of the flotilla with instructions "not to come alongside unless this identity signal is showing".

From that day onward the Captain (S) gave each submarine in his flotilla a Jolly Roger as soon as she had achieved a success on patrol.

[3] On 14 July 1941 Osiris damaged the Italian merchant ship Capo d'Orso (3,149 tons) with gunfire in a surface engagement near Argostolion, Kefalonia, Greece.

In another surface engagement on 27 June 1943, Osiris sank the Italian sailing vessel Vittorina (11 tons) north of Crete (position 36°12'N, 26°45'E) with gunfire.

[2] During the Allied invasion of Sicily from July to August 1943, she was deployed on interception patrol to prevent Italian warships interfering with the landings.