Admiralty tug Admiralty tugs were tugboats built for and operated by the Royal Navy during the 20th century . These were vessels built to Admiralty specifications and in specific classes during the First and Second World War s . They were built to meet the Navy ’ s demand for auxiliary vessels and to supplement the civilian tugs requisitioned by the Admiralty for war service . First World War . At the outbreak of the First World War the RN owned seven tugs , all civilian vessels purchased as required , employed in normal tug duties at naval ports . When war commenced the Admiralty put in train plans to requisition civilian tugs to meet the need for vessels to work as patrol vessels , minesweepers , anti - submarine warfare vessels and a host of routine duties . In all , over 100 civilian tugs were requisitioned in this way . There was an increased need for boats to act on the salvage and rescue of ships attacked and damaged on the high seas , for which the civilian fleet was not sufficient . To meet this need the Admiralty placed an order for 64 sea - going tugs to operate in this capacity . These were to a single design , based on a civilian type , and , as they were built by specialist shipyards , incorporated merchant rather than navy features . However it was specified they be armed and equipped with radio . The main class of Admiralty Tug was the " Saint " class . Of 64 ordered , 46 were completed and commissioned before the end of hostilities . The second class was the " Resolve " ( also called " Rollicker " ) class , 5 large ocean - going tugs for duty on the high seas , but these were incomplete at the war ’ s end . In addition the Admiralty built several classes of small tugs , including 10 " Robust " class paddle tugs , and 6 " West " class harbour tugs , and several classes of tugs for special duties . 15 vessels were built to tugboat design for use as boarding vessels in the Thames estuary and another 13 for use in the Mersey . They also built 24 tugs ( the " Concrete " class ) employed towing ferro - concrete barges between England and France . Second World War . In World War II a similar situation arose ; the Admiralty again requisitioned civilian tugs and placed orders for a range of Admiralty tugs . In all 117 harbour tugs were brought into war service , including the 10 " Robust " and 6 " West " class vessels ( built in World War I and now in civilian service ) and 101 others of various design . Just two harbour tugs were built for the Admiralty during WWII , the " Alligator " class Prior 1939 the RN had built 4 " Brigand " class rescue tugs for its own use ; at the outbreak of World War II a further 74 civilian tugs were requisitioned , including 16 " Saint " and 5 " Rollicker " class of WWI vintage , and 53 others . At the same time orders were placed for 21 Admiralty tugs , the " Assurance " class , the first being delivered in 1940 . In 1942 a further 23 " Favourite " , and 8 " Bustler " class tugs were built , followed in 1944 by 6 " Envoy " class tugs . Most of these vessels were disposed of at the war ’ s end . Current situation . Today the Royal Navy employs a number of tugs as part of the Royal Maritime Auxiliary Service . These include 9 " Adept " class tractor tugs and 2 specialist submarine - berthing tugs . These vessels are operated by civilian crews under contract . Characteristics . Admiralty tugs were built to Navy specifications , and standardized where possible to a single design , though this was based on a civilian type . In this they followed the pattern of other auxiliary vessels , such as the Admiralty trawlers , and the Flower class corvette s . They were built by shipyards specializing in tug construction , and thus incorporated merchant rather than navy features , such as an enclosed bridge , and wooden superstructure . However it was specified they be armed and equipped with radio . The First World War vessels had at least one gun , for self - defence , and smoke - generating gear . In World War II they also carried anti - aircraft guns for protection against air attack . Construction list . One of the builders of these tugs was Henry Robb Ltd . Below is a list of " Bustler Class " Ocean Rescue / Salvage Tugs built during World War II . These were powered by diesel engines . Built and launched in 1941 / 42 were : Built in 1944 / 45 were :