 Force W joined the Harpoon convoy shortly after it entered the Mediterranean on 12 June, and remained with it until turning back, as planned, as the convoy reached the Strait of Sicily on the evening of 14 June.After her return to British waters, "Onslow" formed part of the distant escort for Arctic convoy PQ 17 and the return convoy QP 13.PQ 17 was ordered to be scattered and its close escort withdrawn based on mistaken intelligence that the "Tirpitz" was about to attack the convoy, which resulted in extremely heavy losses to the unprotected merchant ships, with 24 of the 25 merchant ships being sunk by German submarines and aircraft.