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The Light Tank Mk VII 'Tetrarch' (A17) was the last British designed light tank to be used in combat during the Second World War, and saw limited use as a glider-borne aircraft on D-Day and during the crossing of the Rhine.
The Tetrarch marked a total break from the earlier series of light tanks. It was first designed in 1937 as a private venture at Vickers, where it had the designation P.R. The new tank was a major break from the existing line of light tanks, which had reached the Light Tank Mk VI. The most obvious change was the suspension, which had four large road wheels on each side, and no return rollers. An unconventional warp steering system was adopted for high speed but shallow turns, in which the wheels turned, thus distorting the tracks. A more standard braking system was used for sharper turns. The Mk VII had a significantly more modern look than earlier British light tanks, with a larger, centrally mounted turret with sloped sides on top of a superstructure with a sloped front. The prototype was unarmed when it was completed in December 1937, but was later given a 2-pounder gun and coaxial .303in machine gun, a great improvement on the twin machine guns of the Mk VI.
The new design was offered to the War Office in 1938, where it was given the name 'Purdah', allegedly because Vickers had kept it secret for so long. The Mechanisation Experimental Establishment at Aldershot tested the prototype, and its fate was decided at a series of meetings in June 1938. At the time the army was happy with the existing light tanks, so the discussion turned to the idea of using it as a 'light cruiser' tank. The tests had showed that it was slower and worse at crossing obstacles than the existing A.13 Cruiser Tank Mk III, and not worth ordering in that role. However the decision was made to order 70 of the new tank, to follow on after the end of Mk VI production. At a meeting later in the month a number of changes were required, including stronger tracks, larger access doors and better engine cooling.
The type was then given the official designation A.17, and an official specification was issued on 23 June 1938. This called for a three man light tank, with 14mm of armour as standard, a road radius of 200 miles, maximum road speed of 40mph, cross country speed of 22mph, and at this stage an armament of one 15mm anti-tank machine gun and one 7.92mm machine gun in a fully traversing turret. In July the Mechanisation Board submitted its report on the prototype (by then armed with the 2 pdr gun), and recommended that the design should be purchased.
In November 1938 the order for the Tank, Light, Mk. VII, was increased to 120 vehicles, to be delivered in 1940. It was now to be armed with the 2 pounder gun of the prototype and the 7.92mm Besa machine gun called for in the original specification. Production was to be carried out by Metropolitan-Cammell, to keep Vicker's factories free for more urgent projects.
Any urgency soon went out of the Mk VII project. In the aftermath of the retreat to Dunkirk and the success of the German blitzkrieg the General Staff decided that it needed cruiser and infantry tanks to deal with any German invasion. In addition light tanks hadn't been a success in their reconnaissance role, and the decision was made to use armoured cars in the role instead. In July 1940, just as production of the Mk VII was getting under way, the order was cut to only 70 vehicles, Metropolitan-Cammell protested, and it was increased back to 100 on 30 July. Later another 120 were ordered, raising the total to 220, but only 177 were ever completed after the Metropolitan-Cammell works were bombed in April 1941.
Internally the Mk VII was split into three compartments. The driver sat in the centre of the front, with a 22.5 gallon fuel tank on each side. The fighting compartment was in the middle and carried the commander/ loader and gunner. The turret was made of hexagonal flat plates and had hand powered two speed traversing gear. The rear compartment contained the Meadows 12-cylinder flat engine, which was mounted above the gearbox. Some Mk VIIs were given the Littlejohn Adaptor, a reduced bore attachment added to the gun to improve the power of the 2-pounder gun.
The first Light Tank Mk VIIs were delivered in November 1940. By the time the Mk VII entered service, the War Office no longer wanted to use light tanks for reconnaissance, and instead favoured armoured cars. As a result some of the early Mk VIIs went to the armoured divisions rearming in Britain (1st Armoured and 6th Armoured each got one of the first tanks to be delivered), and they were used for training. In July 1941 they were also considered for the Eighth Army in North Africa, but didn't have the right cooling system. In the spring of 1942, by which time the improved supply of cruiser tanks made the remaining light tanks surpluse to requirements, some of the Mk VIIs went to the Soviet Union, and there is photographic evidence that they were used in combat on the Russian Southern Front.
The Mk VII made its combat debut in May 1942 when 'B' Special Service Squadron used the type during 'Operation Ironclad', the Allied invasion of Madagascar, then held by the Vichy French and believed to be vulnerable to a Japanese attack or for use as a naval base. The Mk VII saw very little actual combat during this operation.
The Mk VII was most famous for its use with the airborne forces. The new units needed armoured support, and the Mk VII was small enough to fit in a possible glider, but large enough to be of some use. In 1943 it was give the name 'Tetrarch' (a title used by various rulers in Antiquity). The Hamilcar glider was designed especially to carry the tank, and one airborne reconnaissance regiment, equipped with the tank, became part of the 6th Airborne Division. The first test landing came in April 1944, and despite some incidents were generally successful. Loading the tank into the glider was quite a tricky operation, requiring the undercarriage to be removed to lower the glider to the ground, so the tank could be driven straight in. Unloading was less involved, and was based on the assumption that the undercarriage would probably collapse on landing. If not the oleo legs could be collapsed instead.
On D-Day the 6th Airborne Reconnaissance Regiment, part of the 6th Air Landing Brigade, 6th Airborne Division, was given a mix of Tetrarchs and Universal Carriers (also capable of fitting into a Hamilcar). Eight of the Tetrarchs formed part of the second war air assault, and landed in Normandy on the evening of D-Day. The landings didn’t go well - most of the tanks were put out of action after their tracks got caught up on parachute silks and lines as they were leaving the landing area. They were restored to action after the other half of the tank squadron arrived by sea, but a few days later they were exchanged for Cromwell tanks (always part of the plan).
The Tetrarch was also used during the massive airborne crossing of the Rhine in 1945, although by this point the American M22 Locust had begun to enter service, and played a larger part in the assault.
The Tetrarch remained in use with the airborne forces until 1949-50 (operated by the 3rd Hussars), by which point the gliders needed to carry it into battle had been withdraw.
The Tetrarch was followed into production by the Light Tank Mk VIII 'Harry Hopkins', the last British light tank. This was an improved version of the Tetrarch, but never saw combat.
Variants
Tetrarch ICS (Infantry Close Support)
The Tetrarch ICS was a close-support version of the tank that was armed with a 3in howitzer in place of the 2-pounder gun. Some were produced for use by the airborne forces.
Tetrarch I DD
The Tetrarch was used for early experiments with the Straussler Duplex Drive system. A boat shaped canvas screen was placed around the tank, and the tank engine used to drive a propeller, allowing the tank to swim. The Tetrarch was used for the first successful Duplex Drive trials at the Brent Reservoir in June 1941. These successful trials lead to the adoption of the same technology, first on the Valentine, and later on the Sherman, and this last version was used on D-Day.
Stats
Production: 177
Hull Length: 13ft 6in
Hull Width: 7ft 7in
Height: 6ft 11.5in
Crew: 3
Weight: 16,800lb
Engine: Meadows 12 cylinder 165hp
Max Speed: 40mph (road), 28mph (cross-country)
Max Range: 140 miles (road radius)
Armament: One 2pdr QFSA, One 7.92mm Besa Machine Gun
Armour
Min 4mm Max 14mm