Description
The Mark I was a development of Little Willie, the experimental tank built for the Landships Committee by Lieutenant Walter Wilson and William Tritton in the summer of 1915. Working on problems discovered with Willie, the Mark I was designed by Wilson. A gun turret above the hull would have made the centre of gravity too high, so the guns were put in sponsons. The prototype Mark I, ready in December 1915, was called "Mother". 150 were built. See history of the tank for a fuller story.

Production history
A requirement was found for two types of armament, so Mark Is were armed either with 6 pounder guns and four machine guns and called "Male" (75) or two Vickers machine guns instead of the 6 pounders and called "Female" (75).
To aid steering, a pair of large wheels were added behind the tank. These were not as effective as hoped and were subsequently dropped.
The subsequent Mark II, III, IV and V and later tanks all bear a strong resemblance to their 'Mother'.

Variants
The Gun Carrier Mark I was largely produced with parts identical to those used to build the Mark I.

Crew: 8
Combat Weight

• Male: 28 tons (28.4 tonne)
  Female: 27 tons (27.4 tonne)
  Armour: .23-.47 in (6-12 mm)
  Armament
  
  
  
  • Male: two 6-pounder QF, four 8 mm Hotchkiss Machine Guns
    Female: four .303 Vickers Machine Guns, two 8 mm Hotchkiss Machine Guns Mark I
    Unhardened armour. Built from December 1916 for training only, but used in the Battle of Arras in April 1917 because of delays in the production of the Mark IV. 50 built. Five Mark IIs were used to test transmission types for the new Mark IV.
    
    Mark II
    The Mark III was a training tank, which used Lewis machine guns and a smaller sponson for the females. Fifty were built. It was originally intended that the Mark III have all the proposed new design features of the Mark IV. This is why there were two distinct training types, the Mark II being little more than a slightly improved Mark I. Development of the new features was so slow however, that the change from the Mark II was very gradual only. The last two Mark III's were melted down in World War II.
    
    Mark III
    An up-armoured version of the Mark I with all fuel stored in a single external tank (located between the rear track horns) in an attempt to improve crew safety. The sponsons could be pushed in to reduce the width of the tank for rail transportation. Rails on the roof carried an unditching beam. 1220 were built: 420 Males, 595 Females and 205 Tank Tenders which were supply tanks.
    The director of the Tank Supply Department, Albert Gerald Stern, first intended to fit the Mark IV with a new engine and transmission. Production of battle tanks was halted until the new design was ready, necessitating the Mark II and III as interim training tanks. He failed however to complete development soon enough to start production in time to have 200 tanks ready for the promised date of 1 April 1917. He was ultimately forced to take a Mark IV in production in May 1917 that was only slightly different from the Mark I.
    The Mark IV Male carried 4 Lewis machine guns as well as the two sponson guns (now with shorter barrels). The Female had six machine guns. Two of the machine guns were operated by the gun loaders.
    
    Specs
    Crew: 8
    Combat Weight
    Male: 28 tons (28.4 tonnes), Female: 27 tons (27.4 tonnes)
    Armour: .25-.47 in (6.1 - 12 mm)
    Armament
    
    
    
    • Two MG (Male), Six .303 Lewis MG (Female)
      Ammo storage
      
      
      
      • 6 pounder: 180 HE rounds and remainder Case Mark IV
        
        Mark V series
        The Mark V was first to be a completely new design. When however in December 1917 the desired new engine and transmission became available, this design was abandoned and the designation switched to an improved version of the Mark IV, in fact a Mark IV as it was originally intended: more power (150 bhp) with a new Ricardo engine, improved steering mechanism and epicyclical transmission, only one driver was needed. Cabin for machine-gunner on the roof. 400 were built, 200 each of Males and Females. Several were converted to Hermaphrodites by swapping sponsons to give a single 6 pounder gun for each.
        
        Mark V
        Sir William Tritton in 1917 developed the Tadpole Tail: an extension of the tracks to be fitted to the back of a tank to improve trench crossing abilities. This was necessary because the Hindenburg Line had 3.5 metre wide trenches to stop the British tanks. When Major Philip Johnson of Central Tank Corps Workshops heard of this project, he immediately understood that the weight of the heavy girders strengthening the attachment might be put to a better use by creating a larger tank. He cut a Mark IV in half and stretched the hull, lengthening it by six feet. When details had been forgotten it has for a long time been assumed that most Mark V* had been field conversions made by Johnson. We now know that they were all factory-built. It had a larger 'turret' on the roof and doors in the side of the hull. The weight was 33 tons. 645 were built out of an order for 500 Males and 200 Females.
        The extra section was also designed to house a squad of infantry. This was the first ever purpose designed tracked armoured personnel carrier (APC), it was also the first APC to be significantly armed, as some earlier conversions of tanks into supply carriers lacked any armament. It could operate as a tank as well as carrying troops, and it was not until the post World War II era Merkava that a tank that could also carry troops under protection was produced.
        
        Mark V*
        Because the Mark V* had been lengthened, its original length-width ratio had been spoiled. Lateral forces in a turn now became unacceptably high causing thrown tracks and an enormous turn circle. Therefore Major Wilson redesigned the track in May 1918, with a stronger curve reducing ground contact (but increasing ground pressure as a trade-off). An uprated 225 hp Ricardo engine was fitted. The cabin for the driver was combined with the roof cabin; there now was a separate machine gun position in the back. 197 were built out of an order for 750 Males and 150 Females.
        
        Mark V**
        See: Mark X.
        
        Mark V***
        
        
        Main article: Mark VI (tank) Mark VI
        One of the Mark IIs used as test vehicles had had a hydraulic transmission. In October 1917 Brown Brothers in Edinburgh were granted a contract to develop this line of research further. In July 1918 the prototype was ready. Its drive system was very complex. The Ricardo engine drove into Variable Speed Gear pumps that in turn powered two (Williams-Janney) hydraulic motors, moving one track each by means of several chains. To ward off the obvious danger of overheating there were many fans, louvres and radiators. Steering was easy and gradual however and the version was taken into production to equip one tank battalion. Three were built out of an order for 74 when war ended. The hull was slightly lengthened in comparison with the Mark V. No Mark VIIs survive.
        
        Mark VII
        
        

        Main article: Mark VIII (tank) Mark VIII
        
        

        Main article: Mark IX tank Mark IX
        Paper only project to improve the Mark V, originally known as Mark V***. This was basically a contingency plan in case the Mark VIII project would fail (if so a production of 2000 was foreseen for 1919), trying to produce a tank with as many parts of the Mark V as possible but with improved manoeuvrability and crew comfort.
        
        Mark X
        The first tanks were added, as 'Heavy Branch', to the Machine Gun Corps until a separate Tank Corps was formed on 28 July 1917 by Royal Warrant. A small number of Mark I tanks took part in the battle of the Somme during the Battle of Flers-Courcelette in September 1916. Although many broke down or became stuck, almost a third that attacked made it across no mans land, and their effect on the enemy was noted leading to a request by the British C-in-C Douglas Haig for a thousand more. This came as a bit of a surprise: William Tritton had already started the development of a heavier tank: the Flying Elephant. Unfortunately for the Allies, it also gave the Germans time to develop a specifically designed anti-tank weapon for the infantry, an armour-piercing 7.92 mm bullet. Mark IV tanks were used at the Third Battle of Ypres (Passchendaele) in mid-1917, but without great success due to the mud. Nearly 460 Mark IV tanks were used during the Battle of Cambrai in November 1917, showing that a large concentration of tanks could quickly overcome even the most sophisticated trench system. About forty captured Mark IVs were employed by the Germans as Beutepanzer with a crew of twelve. During the Battle of Amiens in August 1918, Mark V tanks with the new Whippet tank penetrated the German lines in a foretaste of modern armoured warfare. The first tank-to-tank battle was between Mk IV tanks and German A7Vs (see that entry for details).
        Mark V and Whippet tanks were supplied by the British to the White movement during the Russian Civil War; some were subsequently captured by the Red Army. Mark Vs were also delivered to the French, Canadian and American army.
        A Mark V tank can be seen in several photographs taken in Berlin in 1945 in front of the Berliner Dom (Berlin Cathedral). It has been suggested this was a museum piece that had been previously displayed at the Lustgarten and it had been used as a static pillbox to help bolster the city's defences during Nazi Germany's final days. However, there is no evidence this was the case and it is not clear what role (if any) it played in the Battle of Berlin.
        
        Combat history
        A list of preserved tanks:
        
        Surviving vehicles
        
        Little Willie survives at the Bovington Tank Museum; it was saved from being scrapped in 1940 — many other prototypes were melted down during the Invasion Scare — on the pretext it was helping to defend Bovington base against possible German attacks. Little Willie
        
        Male - Clan Leslie. This is the only surviving Mark I and the world's oldest surviving combat tank. It is part of the collection at the Bovington Tank Museum. Little is known of its wartime history, but there are indications it may have served as a driver-training tank. Between 1919 and 1970, it was sited in the grounds of Hatfield House to commemorate the fact this was a testing site for tanks during their earliest development. Mark I
        
        Mark II Female, F53 - The Flying Scotsman, is also at the Bovington Tank Museum. This tank still has battle damage sustained at Battle of Arras in April 1917. Mark II
        
        A Mark IV Female, F4 - Flirt II, which fought at the Battle of Cambrai, is at the Museum of Lincolnshire Life, Lincoln, England. A local company, William Foster & Co., manufactured the first tanks.
        A Mark IV Male, Excellent, is displayed at Bovington.
        A Mark IV Female is preserved at Ashford in Kent. This is one of many that were presented for display to towns and cities in Britain after the war. Most were scrapped in the 1920s and 1930's.
        The Royal Museum of the Army in Brussels has a Male Mark IV tank, the Lodestar III, still in original colours.
        A Mark IV Female, Grit, is displayed in the ANZAC hall at the Australian War Memorial.
        In 1999, a Mark IV Female, D51 - Deborah, was excavated at the village of Flesquières in France. It had been knocked out by shell-fire at the Battle of Cambrai (1917) and subsequently buried when used to fill a crater. Work is underway on its restoration see http://www.tank-cambrai.com/pages/indexpag.html. Mark IV
        
        The Bovington Tank Museum displays a Mark V Male, Number 9199, the only British World War I tank still in working order (several French tanks from that period are still in running condition). It was in action at the Battle of Amiens where its commander was awarded the Military Cross.
        A Mark V** Female - Ol'Faithfull, is also preserved at Bovington.
        A heavily restored Mark V Male, Devil, survives at the London Imperial War Museum.
        Mark V Female - United States Army Ordnance Museum, Aberdeen, Maryland.
        Mark V* Female - Patton Museum of Cavalry and Armor, Fort Knox, Kentucky.
        Mark V - Kubinka Tank Museum, Russia.
        A Mark V serves as memorial in Arkhangelsk. This was originally used by British forces during the Allied Intervention in the Russian Civil War.
        Two preserved Mark Vs, a Male and a Female, form part of an outdoor memorial at Luhansk in the Ukraine; two more are in storage.
        Mark V Female - Kharkiv Historical Museum, Ukraine. Mark V
        
        A modified Liberty tank is preserved at Fort Mead, Maryland.
        A British Mark VIII is at Bovington. Mark VIII/Liberty
        The Bovington Mark II Female tank.
        Mark IV tank at the Museum of Lincolnshire Life.
        Mark IV tank at the Australian War Memorial.
        The Bovington Mark V tank; still in working order.
        The Luhanks Mark V Male tank.
        The Luhanks Mark V Female tank.
        Mark V Male tank at the London Imperial War Museum.
        
        A single vehicle survives at Bovington. It has just been restored. Popular culture