Union Castle’s Durham Castle was completed in February 1904 at Fairfield’s Govan yard, She was built for the Union Castle East Africa service from Cape Town to Mombasa, and was 475 feet long, 8,240grt. During the Great War she primarily remained on her commercial service, occasionally being used as a troopship. She was popular and regular vessel, and was finally withdrawn from service in 1939. Union Castle put her up for disposal, having replaced her with Pretoria Castle. She was purchased in August 1939 by Metal Industries for scrapping at Rosyth.
After the outbreak of World War II, on 2nd October she was acquired by the Admiralty for use as an accommodation ship at Scapa Flow. Some other reports say she was to be used as a store ship or even as a blockship. On 26th January 1940 she was being towed by HMS Watermeyer to Scapa Flow when she hit a mine off Cromarty and sank. The weather was atrocious, with a gale blowing and icy conditions. There were no casualties. The mine was probably laid by the German submarine U57, under Captain Claus Korth.