Vickers 6 - Ton The Vickers 6 - Ton Tank or Vickers Mark E was a British light tank designed as a private project at Vickers . It was not purchased by the British Army , but was picked up by a large number of foreign armed forces and was copied almost exactly by the Soviets as the T - 26 . It was also the direct predecessor of the Polish 7TP tank . By the start of World War II it was the second most common tank design in the world after the Renault FT - 17 . History . The first Mark E was built in 1928 by a design team that included the famed tank designers John Valentine Carden and Vivian Loyd . The hull was made of riveted steel plates , 1 inch ( 25 mm ) thick at the front and over most of the turrets , and about 3 / 4 inch ( 19 mm ) thick on the rear of the hull . The power was provided by an Armstrong Siddeley Puma engine of 80 – 95 horsepower ( 60 – 70 kW ) ( depending on the version ) , which gave it a top speed of 22 mph ( 35 km / h ) on roads . The suspension used two axles , each of which carried a two - wheel bogie to which a second set of bogies was connected with a leaf spring . Upward movement of either set of bogies would force the other down through the spring . This was considered to be a fairly good system and offered better than normal cross - country performance although it could not compare with the contemporary Christie suspension . High strength steel tracks gave over 3000 miles ( 5000 km ) of life which was considerably better than most designs of the era . The tank was built in two versions : The Type B proved to be a real innovation , it was found that the two - man turret dramatically increased the rate of fire of either weapon , while still allowing both to be fired at the same time . This design , which they referred to as a " duplex mounting " , became common on almost all tanks designed after the Mark E . The British Army evaluated the Mark E , but rejected it , apparently due to questions about the reliability of the suspension . Vickers then started advertising the design to all buyers , and soon received a trickle of orders eventually including USSR , Greece , Poland , Bolivia , Siam , Finland , Portugal , China and Bulgaria . A Thai order was placed , but taken over by the British when the war started . Vickers built a total of 153 ( the most common figure ) Mark E ' s . Experience with the Polish machines showed that the engine tended to overheat due to poor airflow over the air - cooled Puma engine . This was addressed by the addition of large air vents on either side of the hull . For a new Belgian order the design was modified to use the Rolls - Royce Phantom II water - cooled engine instead . This engine would not fit in the rear , and had to be mounted along the left side of the tank , requiring the turret to be moved to the right and rearward . One example of the resulting Mark F was tested by Belgium , but rejected . Nevertheless the new hull was used , with the older engine , in the sales to Finland and Siam . The Mark E was also developed as a cargo vehicle , and purchased by the British Army in small numbers as artillery tractor s to haul their large 60 pounder ( 127 mm ) artillery guns . Twelve were ordered by the Army as the " Dragon , Medium Mark IV " ' , while China purchased 23 and India 18 . Poland was generally happy with the design , and purchased 50 and licensed it for local production . Modifying it with larger air intakes , their own machine gun , 360 - degree Gundlach periscope . and a Diesel engine , the design entered service as the 7TP . Only the original 38 entered service , 12 remained unassembled and later used for spares . Out of 38 original two - turreted tanks , 22 were later converted to single turret version with a modified turret and the 47 mm main gun ( Type B standard ) . The Soviets were also happy with the design and licensed it for production . However in their case local production started as the T - 26 , and eventually over 12 , 000 were built in various versions . The Soviet early twin - turret T - 26s had 7 . 62 mm DT machine gun s in each turret , or a mix of one machine gun turret and one 37 mm gun turret . Later , more common versions mounted a 45 mm gun and two DT machine guns . The final versions of the T - 26 had welded construction and , eventually , sloped armor on the hull and turret . Because the T - 26 was in such wide use and was a reliable platform , a variety of engineer vehicles were built on the chassis , including flamethrowers and bridgelayers . A novel radio - controlled demolition tank was built on the T - 26 chassis also . During the Spanish Civil War the Soviet Union sent the T - 26 to the Republican Army . The Italians , after suffering losses from Republican ' s T - 26 during the battle of Guadalajara ( 1937 ) , captured some of these tanks which served as a model for their M11 / 39 and M13 / 40 light / medium tanks . In 1939 , during the Soviet - Finnish Winter War , the Finnish armoured forces consisted of around thirty - two obsolete Renault FT - 17 tanks , some Vickers - Carden - Lloyd Mk . IVs and Model 33s , which were equipped with machine guns , and 26 Vickers Armstrongs 6 - ton tanks . The latter had been re - equipped with 37 mm Bofors AT - guns after the outbreak of the war . Only 13 of these tanks managed to get to the front in time to participate in the battles . At the Battle of Honkaniemi on February 26 , 1940 , the Finns employed their Vickers tanks for the first - and only - time against Russian armour during the Winter War . The results were disastrous . Of the thirteen available Finnish Vickers 6 - ton tanks only six were in fighting condition and able to participate in the first assault on the Soviet lines - to make matters worse , one of the tanks was forced to stop , unable to cross a wide trench . The remaining five continued onwards a few hundred meters but ran into dozens of Soviet tanks in the village of Honkaniemi . The Finnish tanks managed to knock out three Soviet tanks but were soon themselves knocked - out . In the skirmishes that followed , the Finns lost two more Vickers tanks . In 1941 , the Finns rearmed their Vickers 6 - Ton tanks with the Soviet 45 mm gun and re - designated them as T - 26E . These tanks were used by the Finnish Army during the Continuation War . 19 rebuilt Vickers tanks , along with 75 T - 26s continued in Finnish service after the end of the Second World War . Some of these tanks were kept as training tanks until 1959 , when they were finally phased out and replaced by newer British and Soviet tanks .