HMS Medway ( 1928 ) HMS " Medway " was the first purpose - built submarine depot ship constructed for the Royal Navy . She was built by Vickers Armstrong at Barrow - in - Furness during the late 1920s . The ship served on the China Station before the Second World War and was transferred to Egypt in early 1940 . Ordered to evacuate Alexandria in the face of the German advance after the Battle of Gazala in May 1942 , " Medway " sailed for Lebanon at the end of June , escorted by a light cruiser and seven destroyer s . Despite her strong escort , she was torpedoed and sunk by a German submarine on 30 June . Description and construction . " Medway " was designed to support up to 18 and s in peacetime and an additional three submarines during wartime . She carried three QF 4 - inch Mk IV deck guns as spares together with 144 torpedo es to resupply her submarines . The ship proved to be less top - heavy than anticipated and had the enormously high metacentric height of at full load . Built with bilge keels only deep , " Medway " once rolled 42° each way with a period of nine seconds , losing her main topmast . Her bilge keels were subsequently increased in depth to . She was long overall and had a beam of and a draft of . The ship displaced at standard load and up to at ( full load ) . Her crew numbered 400 officers and enlisted men ; she could also accommodate up to 1 , 335 additional men . The ship was powered by MAN diesel engines rated at , driving two shafts , and had a top speed of about . " Medway " carried of diesel fuel for herself and an additional for her submarines . Figures for her range are not available . The ship had five diesel generators for electrical power and special provisions to recharge submarine batteries . She was armed with two low - angle guns in single mounts and four quick - firing Mk V 4 - inch anti - aircraft guns , also in single mounts . The latter guns were controlled by a High - Angle Control System mounted above the bridge . " Medway " was protected by an internal anti - torpedo bulge which incorporated a water jacket of . Amidships a torpedo bulkhead was located 13 feet inboard that inclined outwards above the waterline . The main deck was 1 . 5 inches thick amdiships . " Medway " was ordered on 14 September 1926 as part of the 1925 / 26 Naval Estimates . The ship was laid down in April 1927 by the Vickers Armstrong shipyard in Barrow - in - Furness , launched on 19 July 1928 , and completed on 3 July 1929 . Career . HMS " Medway " served on the China Station before the start of the Second World War , supporting the 4th Submarine Flotilla , and was under refit at Singapore from September 1939 through February 1940 . Upon its completion , she sailed for Hong Kong where she remained until she departed for Alexandria on 2 April . The ship arrived there on 3 May and supported the 1st Submarine Flotilla that operated in the Eastern Mediterranean . Two years later , Vice - Admiral Henry Harwood , Commander - in - Chief , Mediterranean Fleet , ordered all non - essential ships to leave Alexandria in June 1942 as he was preparing to demolish the port facilities there to prevent their capture by the advancing Panzer Army Africa . " Medway " loaded stores and 1 , 135 personnel on 29 June to establish a new base at Beirut , Lebanon and sailed later that day for Beirut . Accompanied by the Greek ship , " Medway " was escorted by the light cruiser and the destroyers , , , , , , and . The next day , off Port Said , the ship was sunk by two torpedoes fired by ; 30 men were lost in the sinking . The British salvaged the wreck and recovered 47 of the 90 spare torpedoes aboard the ship .