Because the "Imperial Star"-class were refrigerated and in merchant shipping terms relatively fast, several sailed in high-risk convoys to relieve the siege of Malta. and took part in Operation Substance in July 1941, "Imperial Star" and were in Operation Halberd the following month, and in August 1942 "Melbourne Star" and served in Operation Pedestal. In February 1942 another ship of the same class, , successfully evacuated an estimated 2,160 people from the fall of Singapore.