Polar Chief was an 8,040 GRT tanker which was built in 1897 as the cargo ship Montcalm. In 1914 she was requisitioned by the Admiralty, serving initially as a troopship. In October 1914, she was converted to a dummy battleship and renamed HMS Audacious. In 1915 she became a depot ship, followed by conversion to a tanker in 1916 when she was sold into Royal Fleet Auxiliary service and renamed RFA Crenella. In 1917, she survived a torpedo attack off the coast of Ireland.