On 27 October 1939 the passenger ship Voltaire of the Lamport & Holt Ltd, Liverpool was requisitioned by the Admiralty and converted to an armed merchant cruiser. Conversion was completed on 4 January 1940.

Displacement: 13245 BRT
Armament: 8x 152mm, 2x 76mm
Speed: 14.5 knots

Career:
January 40 - April 40: Mediterranean Fleet
May 40: Halifax Escort Force
June 40 - March 41: Bermuda and Halifax Escort Force
April 41: South Atlantic Station

On 4 April 1941 HMS Voltaire (A/Capt. James Alexander Pollard Blackburn, DSC, (retired), RN) was on isolated patrol in the central Atlantic, about 900 nautical miles west of the Cape Verde Islands: at 0615 hrs she was spotted by the lookouts of the german raider Thor (Schiff 10, 3862 tgr, 6-150 {5.9"}, 4-21" tubes, FK Kähler) and the ships headed for each other.
At 0645 hrs the opponents opened fire and by 0649 hrs Voltaire was ablaze, by 0715 hrs only 2 guns remained in action and by 0800 hrs she hoisted a white flag, sinking shortly afterwards by the stern with a heavy port list in position 14º30'N, 40º30'W. 75 dead and 197 survivors rescued by the Germans. In the action, Thor expended 724 rounds of 15-cm.