German submarine U - 110 ( 1940 ) German submarine " U - 110 " was a Type IXB U - boat of the German " Kriegsmarine " that operated during World War II . She was captured by the Royal Navy on 9 May 1941 and provided a number of secret cipher documents to the British . " U - 110 " s capture , later given the code name " Operation Primrose " , was one of the biggest secrets of the war , remaining so for seven months . President Franklin D . Roosevelt was only told of the capture by Winston Churchill in January 1942 . Service history . " U - 110 " s keel was laid down 1 February 1940 by AG Weser , of Bremen , Germany as ' werk ' 973 . She was launched on 25 August 1940 and commissioned on 21 November with " Kapitänleutnant " Fritz - Julius Lemp in command . The boat was part of the 2nd U - boat Flotilla from her commissioning date until her loss . Lemp commanded " U - 110 " for her entire career . In an earlier boat ( ) , he was responsible for the sinking of the passenger liner on the first day of the war . The circumstances were such that he was considered for court - martial . He continued , however , to be one of the most successful and rebellious commanders of his day . Operational career . 1st patrol . " U - 110 " set out on her first patrol from Kiel on 9 March 1941 . Her route to the Atlantic Ocean took her through the ' gap ' between the Faroe and Shetland Islands . Her first victim was the " Erdona " which she damaged south of Iceland on 16 March . She also damaged the " Siremalm " on the 23rd . This ship only escaped after she was hit by a torpedo which failed to detonate , ( although it left a large dent ) and the U - boat ' s 105mm deck gun crew forgot to remove the tampion or plug in the muzzle before engaging their target . The resulting explosion on firing the first round wounded three men and compelled the boat to fire on the merchantman with the smaller 37 and 20 mm armament . Despite being hit , " Siremalm " successfully fled the scene , zig - zagging as she went . " U - 110 " arrived in Lorient on the French Atlantic coast on 29 March , having cut the patrol short due to damage from the exploding gun . 2nd patrol and capture . The boat departed Lorient on 15 April 1941 . On the 27th she sank the " Henri Mory " about west northwest of Blaskets Islands , Ireland . Her next quarry were the ships of convoy OB 318 east of Cape Farewell ( Greenland ) . She successfully attacked and sank the " Esmond " and the " Bengore Head " , but the escort vessels responded . The British corvette , HMS " Aubretia " , located the U - boat with ASDIC ( sonar ) . HMS " Aubretia " and British destroyer HMS " Broadway " then proceeded to drop depth charges . Operation " Primrose " . " U - 110 " survived the attack , but was seriously damaged . HMS " Bulldog " and HMS " Broadway " remained in contact after HMS " Aubretia ' s " last attack . HMS " Broadway " shaped course to ram , but fired two depth charges beneath the U - boat instead , in an endeavour to make the crew abandon ship before scuttling her . She surfaced , to the crew ' s relief , and Lemp announced " Last stop , everybody out " , meaning " Abandon ship " . As the crew turned out onto the U - boat ' s deck they came under fire from two attacking destroyers HMS " Bulldog " and " Broadway " with casualties from gunfire and drowning . The British had believed that the German deck gun was to be used and ceased fire when they realised that the U - boat was being abandoned and the crew wanted to surrender . Lemp assumed that the boat , with vents open , would sink , and ordered radio operator Heinz Wilde to leave the codebook s and Enigma machine and get out ; he is reported to have said " the U - boat is sinking " . Another radio operator recovered personal effects , but left the secret material . Lemp realised that " U - 110 " was not sinking and attempted to swim back to it to destroy the secret material , but was never seen again . A German eyewitness testified that he was shot in the water by a British sailor , but his fate is not confirmed . Including Lemp , 15 men were killed in the action , 32 were captured . " Bulldog " s boarding party , led by sub - lieutenant David Balme , got onto " U - 110 " and stripped it of everything portable , including her secret documents and Enigma machine . William Stewart Pollock , a former radio operator in the Royal Navy and on loan to HMS " Bulldog " , was on the second boat to board " U - 110 " . He retrieved the Enigma machine and books as they looked out of place in the radio room . " U - 110 " was taken in tow back toward Britain , but sank en route to Scapa Flow . The documents captured from " U - 110 " helped Bletchley Park codebreakers solve " Reservehandverfahren " , a reserve German hand cipher . Modern - day connections . The 2000 film " U - 571 " was partially inspired by the capture of " U - 110 " . In 2007 , the submarine ' s chronometer was featured on the BBC programme " Antiques Roadshow " , from Alnwick Castle , in the possession of the grandson of the captain of the ship which captured her .