During the Second World War she helped escort 21 Arctic convoys, and participated in Operation Neptune. She was also involved in the accidental sinking the Polish submarine ORP Jastrząb, along with HNoMS St Albans, during the passage of Arctic convoy PQ 15. Five crewmen were killed. A court of Enquiry found that Jastrząb was 100 miles out of position, in an area where U-boats were expected to operate, and no blame could be attached to either commander. However, other sources maintain the convoy changed its course and entered Jastrząb's patrol sector. Also that the Allied ships ignored identification marks, while on surface, and that Seagull's commander was later found guilty by the Admiralty. These accounts are not reconcilable.