Ernest Martin Jehan Ernest Martin Jehan DSC ( 2 February 1878 – 7 December 1929 ) was an officer in the Royal Navy during the First World War . Jehan is best known for the sinking of a German submarine by he and his crew aboard the smack " Inverlyon " . He began the war as a warrant officer and was decorated and commissioned after sinking UB - 4 . Early life and career . Born in Forest , Guernsey on 2 February 1878 , Ernest Martin Jehan had worked as a plasterer before joining the Royal Navy on 8 February 1894 , when he reached the age of eighteen he signed up for 12 years service initially . At the age of 18 , he was described as being with dark brown hair , brown eyes and a " dark " complexion . Jehan ' s first posting on 4 February 1894 was to the stone frigate HMS " Impregnable " , then based on the former HMS " Howe " , where he was rated boy seaman . He was then moved to HMS " Boscawen " ( on the former HMS " Trafalgar " ) on 22 February 1895 , then HMS " Victory I " on 10 July 1895 and HMS " Australia " on 12 September 1895 , where on turning eighteen he was rated ordinary seaman . He briefly returned to " Victory I " from 6 February before being posted to HMS " Fox " on 14 April 1896 . He was rated able seaman on 11 June 1896 , when he also began specialist gunnery training . Jehan was posted to HMS " Duke of Wellington I " on 8 July 1899 , and was rated leading seaman on 28 October 1899 . He then transferred to the naval gunnery school HMS " Excellent " on Whale Island on 5 December 1899 , and then briefly to the torpedo school HMS " Vernon " in September 1900 , before returning to " Excellent " on 25 November . He was posted to HMS " Duke of Wellington " on 2 December HMS " Raven " on 9 December and back to " Duke of Wellington I " on 26 March 1901 . He joined HMS " Eclipse " on 30 May 1901 and was rated petty officer 2nd class on 14 October . He returned " Excellent " 8 April 1903 , and was rated petty officer 1st class on 17 June 1904 . He briefly went back to " Vernon " on 28 June before returning to " Excellent " on 10 November . He was posted to HMS " Sappho " on 1 December 1904 . Jehan was then promoted to acting gunner ( a warrant rank ) on 11 April 1905 . He served as an interpreter during a visit to Portsmouth by the French fleet in August 1905 but failed a preliminary French exam in October that year . His rank was confirmed on 2 April 1906 . He was largely employed on training duties in various establishments around Portsmouth until on 11 July 1910 , he was appointed to the crew that took the light cruiser to Canada , one of two warships purchased by Canada from the British Admiralty . There he remained aboard the Canadian cruiser at Esquimalt , British Columbia , until ordered back to England in 1913 , arriving back on 19 November . On 4 April 1914 , just prior to the outbreak of the First World War , Jehan was posted to HMS " Dryad " , a torpedo boat converted into a minesweeper . From " Dryad " he was sent to " Inverlyon " as the commanding officer . Action of 15 August 1915 . The Action of 15 August 1915 was a small naval battle involving Ernest Jehan . In 1915 , the German Empire had begun its first U - boat campaign of the First World War . U - boats operated all around the British Isles , attacking allied warships and merchant vessels . The allies therefore began conducting counter submarine activities . One of the first counter measures to be taken was the deployment of Q - ships , merchant ships armed with hidden heavy weapons to lure out and destroy German submarines . " Inverlyon " , a fishing smack , was one of these vessels . Fitted with a 3 - pounder and commanded by Jehan , " Inverlyon " sailed for enemy infested waters . While sailing off the coast of Great Yarmouth on 14 August 1915 , Gunner Jehan received news that a merchant ship , the " Bona Fide " , of 59 tons , had been stopped by the German submarine UB - 4 and subsequently scuttled with explosive s by a boarding party . By the next day Ernest had rushed to the " Bona Fide " ' s last known position , at about 20 : 20 hours , The German sub surfaced near the " Inverlyon " . Then from the submarines conning tower came the shouts from a German sailor ordering " Inverlyon " s crew to prepare for boarding . Naturally the Q - ship disregarded the German officer ' s order . Jehan waited until the submarine came to 30 yards ( 27m ) away when he gave the command to raise the White Ensign and open fire . A series of three rounds from the sailing ship ' s gun struck the U - boat ' s conning tower and bridge , disabling the German commander . UB - 4 then drifted behind " Inverlyon " , where her gun crew fired another six shots into UB - 4 ' s hull while others raked the sub with small arms fire . The U - boat then began to take on water from the bow area ; the submarine was almost vertical before slipping beneath the waves and getting caught on " Inverlyon " s fishing net . Because the submarine was caught on " Inverlyon " s net , Jehan sent a message home asking if the submarine should be raised and salvaged . The Admiralty replied with a negative response so the net was simply cut , allowing UB - 4 to finish sinking to the bottom . All of the crew and commanding officer , Lt . Karl Gross , were killed . As result of the battle , Ernest Martin Jehan was awarded the Distinguished Service Cross on 19 November 1915 , and promoted to lieutenant . After " Inverlyon " s Cruise . By 1916 , Jehan was relieved of the " Inverlyon " and sent to HMS " Sarpedon " as the executive officer . Later he commanded HMS " PC - 55 " from 1919 to 1920 and retired on 29 October 1920 . Jehan died on 7 December 1929 aged fifty - one . Notes . Due to " Inverlyon " s sinking of the UB - 4 , Jehan became the first and only commander to sink a modern steel submarine with a sailing vessel . Daniel Herbert Jehan , who was possibly Ernest ' s twin brother , was also awarded the Distinguished Service Cross for his actions in the war . Ernest ' s son , Ernest Frederick Jehan went on to fight in the Second World War .