Arthur Hezlet Vice - Admiral Sir Arthur Richard " Baldy " Hezlet , KBE , CB , DSO and Bar , DSC , Legion of Merit ( United States ) ( 7 April 1914 – 7 November 2007 ) was a decorated Royal Navy submarine r . He became the Royal Navy ' s youngest captain , aged 36 , and its youngest admiral , aged 45 . In retirement he became a military historian . Early life . Hezlet was born in Pretoria , South Africa , where his father Major - General RK Hezlet , CB , CBE , DSO , was serving in the British Army . Hezlet joined the Royal Navy in January 1928 , aged 13 . He attended the Royal Naval College , Dartmouth and the Royal Naval College , Greenwich , and went to sea in 1932 , serving as a midshipman on the battleship s HMS " Royal Oak " and HMS " Resolution " . By 1936 , he was the correspondence officer on the destroyer HMS " Daring " , later volunteering to serve on submarine s . He served on HMS " Regulus " . Second World War . Hezlet was serving on the submarine HMS " H43 " at the outbreak of the Second World War , but quickly became First Lieutenant aboard the submarine HMS " Trident " . By early 1940 , he was engaged in operations in the Norwegian Sea , as the Germans launched their occupation of Norway . He was mentioned in dispatches . Following the military disaster in Dunkirk , " Trident " was re - positioned in the English Channel to assist in repulsing an expected German attempt at invasion of mainland Britain . In 1940 , Hezlet passed the " perisher " exam to become a submarine commanding officer , and took command of the obsolete coastal submarine HMS " H44 " in December . He was then sent to Malta as a " spare CO " . He commanded the submarine HMS " Unique " , one of the " Fighting " 10th Submarine Flotilla based in Malta from 1941 to 1944 . The flotilla helped sink over 1 , 000 , 000 tonnes of Axis shipping . Hezlet was awarded the DSC for sinking the 11 , 000 tonne Italian troopship " Esperia " . He also commanded HMS " Ursula " on six patrols , and HMS " Upholder " on one patrol . Hezlet returned to the UK in September 1941 , with Ian McGeoch as his first lieutenant , to take command of " Trident " again . In May 1942 , he was involved in protecting convoys to North Russia . He sank the German ore carrier " Hoedur " , and picked up survivors from sunk merchant vessels . He also operated on the surface as escort vessel for the large convoy PQ16 , and was mentioned in dispatches again . He became a special training officer on the banks of the River Clyde in September 1942 , at the informally named " HMS Varbel " , training the crews of midget submarine s to attack the German battleship " Tirpitz " . He invented the " Hezlet Rail " , bar and strap that kept men aboard the vessel . He was mentioned in dispatches after commanding the towing submarine HMS " Thrasher " . Hezlet then took command of the submarine HMS " Trenchant " , based at Trincomalee , Ceylon ( now Sri Lanka ) . He undertook long - range patrols in the Indian and Pacific oceans , earning him his first Distinguished Service Order ( DSO ) . He sunk the long - range German U - boat U - 859 , on 22 September 1944 , near the Sunda Strait , as a result of Enigma intelligence information . The " Trenchant " also sank numerous Japanese submarine chaser s , landing craft , coasters and a minelayer . His crew conducted the last attack by two - man " chariot " submarines , on the Japanese - held harbour of Phuket in Thailand . On 8 June 1945 , Hezlet took " Trenchant " into shallow mined water in the Banka Strait off Sumatra , to intercept Japanese heavy cruiser " Ashigara " . Despite being attacked by the Japanese destroyer " Kamikaze " , five out of eight torpedoes that he fired hit " Ashigara " , which quickly sank . It was the largest Japanese warship sunk by a Royal Navy warship during the war . Hezlet was ordered to Subic Bay in the Philippines , where he was awarded the U . S . Legion of Merit by U . S . Admiral James Fife , Jr . . He was also awarded a bar to his DSO . Ordered to return to the UK , he ended the war as he began it , serving on a submarine . Post - war career . After the war , Hezlet attended naval and three - service staff college s . In 1946 , he was one of a small group of Britons permitted to observe the U . S . nuclear bomb tests at Bikini Atoll . He commanded the destroyer HMS " Scorpion " , and then served in the Admiralty , and as Chief Staff Officer to the Flag Officer Submarines , before taking command of the destroyer HMS " Battleaxe " and becoming Captain D of the 6th Destroyer Flotilla in 1955 . In 1956 , Hezlet was appointed as Director of the Naval Staff College at Greenwich . After commanding the cruiser HMS " Newfoundland " , he was appointed as Flag Officer Submarines and promoted to rear admiral in 1959 , aged 45 , a post he held for 3 years . The submarine HMS " Dreadnought " , Britain ' s first nuclear attack submarine , was launched in early 1960 . The task of the Flag Officer Submarines was to help formulate plans for support and training facilities in a force as yet unfamiliar with nuclear propulsion . He was also in office later that year , when the preferred option for the UK ' s nuclear deterrent moved from the air - launched Skybolt missile to the Polaris missile launched by ballistic missile submarine s . He was appointed CB in 1961 . Hezlet ' s final tour was Flag Officer Scotland and Northern Ireland ( FOSNI ) . He was promoted to vice - admiral and appointed KBE before his retirement in 1964 . Later life . Hezlet returned to his family home , Bovagh House , at Aghadowey in County Londonderry . He was Northern Ireland president of the Royal British Legion for 25 years . He also served with the RNLI , a member of the general synod of the Church of Ireland , and was an original council member of the University of Ulster . He was a keen yachtsman , and his yacht Agivey was a familiar sight on the coast of Ireland and Scotland . He was appointed High Sheriff of County Londonderry for 1968 . Hezlet died at Bovagh , at the age of 93 , in 2007 . He was survived by his wife , Anne Joan Patricia Clark whom he married in 1948 , and their two daughters . Writings . In retirement , Hezlet wrote many books on naval matters . His first book , " The Submarine and Sea Power " ( 1967 ) , foresaw the continuing invulnerability of the seaborne nuclear deterrent . In " Aircraft and Sea Power " ( 1970 ) , he took the view that the Atlantic could be defended by land - based aircraft and submarines , with no surface vessels . Hezlet also wrote a history of the Ulster Special Constabulary , the " B Specials " , in 1972 . He reviewed the use of electricity and electronics in naval warfare in " The Electron and Sea Power " ( 1976 ) . He published a memoir , " HMS Trenchant at War : from Chatham to the Banka Strait " , in 2001 , and his last book , the authoritative " History of British and Allied Submarine Operations " ( 2002 ) , listed every patrol taken by an Allied submarine in the Second World War .