On 16 March 1917, "Achilles" and the armed boarding steamer were patrolling north of the Shetland Islands when they encountered the disguised German auxiliary cruiser "Leopard". The latter ship heaved to when commanded, but manoeuvred to prevent "Dundee" from boarding her and then fired two torpedoes which missed. "Dundee" retaliated by raking "Leopard"s stern, badly damaging the German ship and then "Achilles" opened fire herself. The German ship sank an hour later with no survivors. "Achilles" was transferred to the North America and West Indies Station in August 1917 for convoy escort duties, but returned to Britain for a refit between February and December 1918. Upon completion of this refit "Achilles" became a stoker's training ship at Chatham. The ship was sold for scrap on 9 May 1921.