HMS Graph was a German Type VIIC U-boat used by the British Royal Navy during World War II. Commissioned as the U-570 in the German Kriegsmarine in mid-1941, she was attacked and captured on her first patrol.She provided both the Royal Navy and United States Navy with significant information on German submarines, and carried out three combat patrols with a Royal Navy crew, becoming the only U-boat to see active service with both sides during the war. She was withdrawn from service in 1944 due to problems maintaining her. While being towed to the breakers for scrapping, she ran aground on an island off the west coast of Scotland. Some of the wreck was removed as scrap but some wreckage remains there to the present day.Design and constructionThe submarine was built to the German Type VIIC design. She had a displacement of 769 tonnes (757 long tons) when surfaced, and 871 t (857 long tons) when submerged. The boat was 67.1 metres (220 ft 2 in) long, with a beam of 6.2 metres (20 ft 4 in), and a draught of 4.74 metres (15 ft 7 in). The diesel-electric propulsion system provided a maximum speed of 18.8 knots (34.8 km/h; 21.6 mph) surfaced or 7.6 knots (14.1 km/h; 8.7 mph) submerged. The U-570 had a fuel capacity of 109 long tons (111 t) which gave a range of 7,500 nautical miles (13,900 km) at 10 knots (19 km/h; 12 mph). The test depth of the submarine was 230 metres (750 ft).