After the First World War Britain disbanded most of its tank units leaving only five tank battalions equipped with the Mark V and the Medium Mark C.
At first a large budget was made available for tank design but this was all spent on the failed development of the Medium Mark D.
The first prototype was a "Female" version with three Hotchkiss machine guns; the second prototype was a "Male" which had a 3-pounder gun in place of one of the machine guns and also a machine gun for anti-aircraft use. It looked far closer to a modern tank than its predecessors with the turret, the front of the fighting compartment and the hull front plate all strongly rounded. The advanced transmission proved to be utterly unreliable however and the project was abandoned in 1922 in favour of a generally more conventional design, the Vickers Light Tank Mark I. This would be renamed the Vickers Medium Tank Mark I in 1924 . The first prototypes were sent to Bovington for trial in 1923. The Vickers designation was A2E1.
Despite being in general more conventional, in one aspect the Medium Mark I looked rather modern: instead of a high track run it possessed a low and flat suspension system with five bogies, each having a pair of small double wheels. The axles of these were too weakly constructed; as Major-General N.W. Duncan put it in his Medium Marks I-III: "(...) a perpetual nuisance. The axles were continually breaking and the path of the Mark I tanks was littered with discarded wheels". This was cured by switching to a "box bogie" in 1931. To ease repairs the suspension was not protected by an armoured covering. There were two vertical helical springs of unequal length in each of the five bogie casings attached to the hull. In front and behind the normal ten road wheel pairs, there was a tension wheel pair. Ground pressure was very high, even though at 11.7 long tons the vehicle was not very heavy for its size.
The engine was an air-cooled 90 hp Armstrong Siddeley engine derived from an aircraft type. Surprisingly the engine and transmission was distributed throughout the hull - with the engine to the left of the driver, the gearbox underneath the commander and final drive at the rear, which Duncan describes as "an unbelievable retrograde step in view of war-time experience". The Medium Mark B and the Mark VIII had introduced compartmentalisation to reduce the debilitating effects of engine noise and fumes on the crew. However with the Medium Mark I considerations of ease of maintenance took precedence.
The petrol tanks were at the very rear of the hull, so the fuel lines had to run along the whole length of the vehicle, pumping fuel to a secondary tank that fed the engine by gravity. The engine was lubricated and partially cooled by oil; leakage was common and the original four-gallon reservoir had to be replaced by a 13.5 one. The tank could be electrically started, but only if the motor was already warm, so the first start had to be done by hand from the inside of the vehicle. Maximum speed was about 15 mph and the range about 120 miles.
Except for the Lago prototype, a predecessor to the Stridsvagn m/42, produced by Landsverk in 1934 no other manufacturer constructed a tank with a three-man turret until the German Panzer III. The practical importance of this feature is signified by the fact that later into the World War II, most of both sides tanks' designs either quickly switched to the three-man turret, or were abandoned as obsolete.
There was no co-axial machine gun. There was only room to operate one machine gun from the turret; normally one gun was switched between the respective mountings as the guns were removable. The turret machine gunner doubled as main gun loader. In each side of the hull was a Vickers machine gun. There was one gunner to operate these, he also functioned as a mechanic.
The shape of the Mark I Medium hull was very distinctive. The back was a simple armoured box; the front plate was high and perfectly vertical. Between them, from the armoured hood of the driver at the right of the vehicle six armour plates fanned out to the left, making for a complex hull geometry at that side. In all the tank made an ungainly squat impression. The crew of five was only poorly protected by 6.25 mm plating, rivetted to the chassis, barely enough to counter the threat posed by light machine guns. With its many shot traps the vehicle was unable to withstand even anti-tank rifle fire and it had a high profile. The internal lay-out worsened this vulnerability as the petrol tanks were inside the main compartment.
The Medium Mark I replaced some of the Mark V heavy tanks; together with its successor, the slightly improved Vickers Medium Mark II, it served in the Royal Tank Regiments, being the first type of the in total 200 tanks to be phased out in 1938.
The Medium Mark I was the first tank to see "mass" production since the last of the ten Char 2C's had been finished in 1921. Indeed, as of the next tank, the Renault NC27, only about thirty were built, the British Mediums represented most of the world tank production during the Twenties. They never fired a shot in anger and their performance in a real battle can only be speculated upon but as the only modern tanks in existence in the decade after the First World War they provided the British with a unique opportunity to test the many new ideas about mechanised warfare using real operational units. The knowledge thus gained would prove invaluable in the Second World War
|Vickers Medium Mark I|
Vickers tanks on the move in England in the 1930s
|Place of origin||United Kingdom|
|Specifications (Mk I)|
|Weight||11.7 long tons|
|Length||17 ft 6 in (5.33 m)|
|Width||9 ft 1.5 in (2.781 m)|
|Height||9 ft 3 in (2.82 m)|
|QF 3 pounder gun (47 mm)|
|Vickers machine guns|
|Engine||Armstrong Siddeley V-8 air-cooled petrol engine|
90 hp (67 kW)
|Transmission||4-speed gearbox to a 2-speed epicyclic|
|120 mi (190 km)|
|Speed||15 mph (24 km/h)|
Medium Mark IA*: the original tank turrets were rebuilt and upgraded by removing the Hotchkiss mountings, installing a co-axial Vickers machine gun, compensating for its weight with a lead counterweight at the back of the turret and putting the Bishops's Mitre on top of it, a traversable cupola.
Medium Mark I CS and Medium Mark IA CS: a dozen tanks were rebuilt as close support vehicles, mainly for smoke laying, equipped with a 15-pounder mortar.
Experimental Wheel and Track Medium Mark I: this was a wheel-cum-track project of 1926 to improve strategic mobility. The tank could be elevated by jacks on four enormous rubber-tyred wheels, two to be lowered at its extremes, the front ones steerable. The back ones could be driven, making the vehicle look "rather like a house perched on a very inadequate roller skate"; more practical was to tow it by a truck. This vehicle was also equipped with an experimental driver's hood. The contraption was later removed.