G and H - class destroyer The G - and H - class destroyers were a class of twenty - four destroyer s of the Royal Navy ( two later transferred to the Royal Canadian Navy and one to the Polish Navy ) launched in 1935 – 1939 . They served in World War II and sixteen were lost , with a seventeenth being written off as a constructive total loss . Other ships were built for the navies of Argentina , Brazil , and Greece . Design . G class . The G class were ordered as part of the 1933 naval construction programme , the H class following in 1934 . They were generally repeats of the preceding F class , with a slight reduction in dimensions by the reduction of cruising turbines . Armament in the Gs was same as the Fs , based on the 4 . 7 inch QF Mark IX as the main gun . The 40° elevation of the guns in the CP ( central pivot ) Mark XVII mounting was achieved by building a lowered section of the deck , the " well " , that allowed the breech of the gun to be lowered below deck height . " Glowworm " trialled the new quintuple PR Mk . I torpedo tubes , her sisters retaining the quadruple Mk . VIII . All G - class ships had tripod foremasts and pole mainmasts . H class . The H class were repeats of the Gs , but a more satisfactory solution was found to achieve the gun elevation , by rearranging the breech end of the guns , the mountings CP Mk . XVIII could elevate to 40° without the need for the deck wells . Despite the availability of the quintuple tubes as trialled in " Glowworm " , these were not fitted due to topweight concerns . Design improvements and the increased use of welding resulted in a decrease in displacement of some 50 tons . " Hero " and " Hereward " saw the introduction of a new style of bridge that would become standard on all Royal Navy fleet destroyers from the I class through to the Battle class of 1944 . This was necessary as " Hereward " carried a prototype twin gun mounting CP Mark XIX that was to be fitted to the Tribal and the J , K and N classes . This weapon had a trunnion height 13 inches higher than the previous weapons , therefore it was necessary to raise the wheelhouse to allow the helmsman to see over the top . Raising the wheelhouse meant it had to be placed in front of , rather than underneath , the bridge , and it was given sloping , armoured faces , resulting in a characteristic wedge shape , with a sloping roof to give the bridge a view over the fo ' c ' sle . Internally , the H class were as per the G class , except " Hyperion " , which received a single Johnson type boiler that was both smaller , lighter , and more economical than the Admiralty design . All ships had pole masts fore and aft and were fitted with TSDS ( Two Speed Destroyer Sweeps ) minesweeping gear . Flotilla leaders . As per the E and F class , the flotilla leader s were built to an enlarged design , incorporating a fifth 4 . 7 inch gun in ' Q ' position , between the funnels . They were based on the F - class leader , " Faulknor " . " Grenville " was slightly shorter as she used compact Yarrow - type side fired boilers . " Hardy " could be identified by having a tripod foremast . Both ships were early wartime losses and consequently received no modifications . " Havant " class . The " Havants " were laid down in 1938 for Brazil . They had pole masts forward and tripods aft , were completed without ' Y ' gun on the quarterdeck , allowing an increase in depth charge stowage , and with the funnels cut down to improve the field of fire for A / A weapons . They were completed with rangefinders only , but later shipped the designed combined rangefinder - director on the bridge , as opposed to the separated functions of their half sisters . After commissioning into the Royal Navy , " Handy " and " Hearty " were renamed " Harvester " and " Hesperus " respectively to avoid confusion with " Hardy " . The six " Havant " - class destroyers initially formed the 9th Destroyer Flotilla of the Home Fleet assigned to anti - submarine protection of Scapa Flow . In late 1940 , 9th Destroyer Flotilla was transferred to the Western Approaches Command and re - designated 9th Escort Group . In March 1942 , the remaining five " Havant " - class destroyers were designated group leaders of the Mid - Ocean Escort Force through the winter of 1942 - 43 . " HMS Hurricane " was leader of Escort Group B - 1 for convoys HX - 187 , ONS - 96 , HX - 193 , ONS - 108 , SC - 92 , ON119 / HX - 201 , ONS - 124 , HX - 206 , ONS - 134 , SC - 105 , HX - 215 , ON - 151 , SC - 114 , ON - 162 , SC - 119 , ONS - 171 , HX - 230 , ON - 178 and HX - 236 . " HMS Hesperus " was leader of Escort Group B - 2 for convoys SC - 81 , ON - 97 , SC - 86 , ON - 107 , HX - 198 , ONS - 118 , HX - 203 , ONS - 128 , HX - 208 , ONS - 138 , HX213 , ONS - 148 , HX219 , ON - 159 , SC - 118 , ON - 170 , SC - 123 , ONS - 4 , SC - 129 and ONS - 9 . " HMS Harvester " was leader of Escort Group B - 3 for convoys HX - 188 , ONS - 98 , HX - 194 , ONS - 110 , SC - 93 , ON - 121 / HX - 202 , ONS - 126 , HX - 207 , ONS - 136 , SC - 106 , ONS - 146 , HX - 218 , ON - 157 , SC - 117 , ONS - 167 , and was sunk while escorting HX - 228 . " HMS Highlander " was leader of Escort Group B - 4 for convoys SC - 82 , ON - 99 , SC - 87 , ON - 109 , HX - 199 , ONS - 120 , HX - 204 , ONS - 130 , HX - 209 , ONS - 140 , HX - 214 , ONS - 150 , HX - 220 , ON - 161 , ONS - 169 , HX - 229 , ON - 176 , HX - 234 , and ON - 183 . " HMS Havelock " was leader of Escort Group B - 5 in the Caribbean until escorting convoys ON - 168 , SC - 122 , SC - 126 and ONS - 7 . Ships . Royal Navy . " Havant " class . These six ships were ordered by the Brazilian Navy but on the outbreak of World War II they were requisitioned by the Royal Navy . They are usually included with the H class . Argentine Navy . Seven ships were built for the Argentine Navy as the " Buenos Aires " class , they were delivered in 1938 . They were built by Vickers Armstrongs ( Barrow ) , Cammell Laird and John Brown & Company ( Clydebank ) . Brazilian Navy . Brazil ordered six " Jarua " - class ships from Britain in 1938 . These ships were purchased by Britain on the outbreak of war in 1939 and are described above . The Brazilians decided to produce indigenous destroyers , the , at the Ilha das Cobras shipyard , Rio de Janeiro . The design was based on the H - class plans supplied by Britain , but with guns and machinery supplied by the USA . Although laid down in 1940 , the ships were not completed until 1949 – 51 . Royal Hellenic Navy . Two ships , modified versions of the G class , were built for the Greek Royal Hellenic Navy by Yarrow . The ships were fitted with German - made 12 . 7 cm SK C / 34 naval gun s and 37 mm AA guns . The installation of the armament was carried out in Greece as the Germans refused to ship the weapons to Britain . Two further ships , the " Vasilefs Konstantinos " and " Vasilissa Sofia " , named after King Constantine I and Queen Sofia respectively , were to be built in Greece , but construction halted due to the outbreak of the Second World War .