The Tank, Infantry, Mk II was designed at the Royal Arsenal, Woolwich, and built by Vulcan Foundry, as an improvement on the Mk I which was a two man tank with only machine guns for armament. The Senior Matilda weighed 27 metric tons, more than twice as much as its predecessor, and was armed with a QF 2-pounder tank gun in a three-man turret.

Like other infantry tanks it was heavily armoured; from 20 mm at the thinnest it was 78 mm (3.1 inch) at the front, much more than most contemporaries. The weight of the armour, together with the relatively weak twin-engine power unit (adapted from a bus) and troublesome suspension severely limited the speed of the vehicle. For example, in the deserts of North Africa the Matilda could average only about 9.5 km/h. This was not thought to be a problem because the Matilda was specifically designed in accordance with the British doctrine of infantry tanks, that is, slow-moving, heavily-armoured vehicles designed to provide support to infantry. Under this thinking, a speed equal to the walking speed of a man was considered sufficient. Only combat would prove that the doctrine was flawed. The heavy armour of the Matilda's cast turret became legendary; for a time in 1940-41 the Matilda earned the nickname "Queen of the Desert".

The Churchill Crocodile was a British flame-throwing tank of late World War II, it was a variant of the Tank, Infantry, Mk VI (A22) Churchill VII, although the Churchill IV was initially chosen to be the base vehicle. Eight hundred were built.

It was introduced as one of the specialised armoured vehicles developed by Major-General Percy Hobart (Hobart's Funnies) and produced from October 1943, in time for the Normandy invasion. The Crocodile kept its 75 mm gun in the turret, and the hull mounted machine gun was replaced by the flame-thrower.

Four hundred gallons of fuel and nitrogen propellant, enough for eighty one-second bursts, were stored in a 6½ ton detachable armoured trailer towed by the Crocodile. The thrower had a range of up to 120 yards (some sources quote 150 yards). The pressure required had to be primed on the trailer by the crew as close to use as feasible, because pressure could not be maintained for very long.

Used by the 79th Armoured Division in concert with the Churchill AVRE, the Crocodile was an effective assault weapon whose threat could induce enemy troops to retreat or surrender. The Crocodile was a specialised weapon, best used against suitable targets. Aspects of the mechanism were considered by the British to be so secret that disabled units, if they could not be recovered, were rapidly destroyed by any means, if necessary, by air strike.

British crewed Crocodiles supported the U.S. Army in the Normandy bocage and, later, during Operation Clipper, the Anglo-American assault on Geilenkirchen.

In 1938, the War Office had issued a requirement for a new, better armoured cruiser tank to replace the Cruiser IV. Nuffield's A16 design was found to be too expensive and in 1939 a cheaper A13 Mk III was adopted. London, Midland and Scottish Railway Company (LMSR) designed the hull, Nuffield - the turret and Henry Meadows - the engine. On April 17, before even a single prototype was produced, first 100 vehicles were ordered from the LMSR and soon additional orders followed, with English Electric and Leyland Motors joining the production effort, a total of 1,771 Covenanters were produced. Nuffield was also approached, but preferred to design its own offspring of the A13 line, which became the Cruiser Mk.VI Crusader.

In an attempt to keep the vehicle as low as possible, a low profile horizontally opposed engine was used. However, that left no room for radiators in the engine compartment. As a result, the radiators were moved to the front of the vehicle. The unusual arrangement, combined with rushed design process, resulted in serious problems with engine cooling. These problems meant that the Covenanter could not be employed in the North African Campaign. Instead, Crusader and American tanks were sent to Africa, while all 1,700 Covenanters produced remained in the British Isles.

By late 1943 the Covenanter was considered too weakly armed and armoured to deal with new German tanks. It was decided that neither problem could be addressed without significant changes in the design, so the tank was declared obsolete and all vehicles except the bridgelayer variant were scrapped.

Except for a few vehicles, Covenanters were never deployed outside of the British Isles. The British 1st Armoured Division was equipped initially with them, but when it was sent to Egypt, the tanks were transferred to the 9th Armoured Division. Eventually a handful of vehicles were sent to the desert for service trials. It is not clear if these tanks were ever used in combat. Covenanters were also issued to some Polish units formed in the UK; they were replaced before these units were sent to the frontline. The only Covenanter known to have been lost to enemy action was destroyed by a German air raid on May 31, 1942 in Canterbury.

A few bridgelayers were used by the Australian forces in the Pacific Campaign.

In 1939, the U.S. Army possessed few tanks or viable tank designs. The interwar years had been a time of small budgets for tank development. The United States had no infrastructure for tank production, little experience in tank design, and little doctrine to guide design efforts.

In this context the M2 series medium tank was developed. Though typical of tanks of many nations when first produced in 1939, by the time the U.S. entered the war the M2 design was obsolete with only a 37 mm gun, about 30 mm armor, and a very high silhouette. The success of tanks such as the Panzer III and Panzer IV in the French campaign, prompted the U.S. Army to rethink their designs. The U.S. Army immediately issued a requirement for a new medium tank armed with a 75 mm gun in a turret. This eventually became the M4 Sherman. However, until the Sherman could be ready for production, an interim design with a 75 mm gun was urgently needed.

The M3 was the interim solution. The tank design was unusual in that the main weapon, a larger caliber, lower-velocity 75 mm gun was in an offset sponson mounting in the hull, with consequent limited traverse. A small turret with a lighter, higher-velocity 37 mm gun was on the top of the tall hull. A small cupola on top of the turret held a machine gun giving the effect of one turret on top of another. The use of two main guns was seen on tanks like the French Char B, the Soviet T-35, and the Mark I version of the British Churchill tank. In each case, two weapons were mounted to give the tanks adequate capability in firing both anti-personnel high explosive ammunition (which needed to contain large amount of explosives) and armor-piercing ammunition for anti-tank combat (with efficiency depending on a kinetic energy of the projectile). The M3 differed slightly from this pattern by using a main gun which could fire an armor-piercing projectile at a velocity high enough for efficiently piercing armor, as well as deliver a high-explosive shell that was large enough to be effective. By using the hull mount, the M3 design was brought to production quicker than if a proper turreted mount had been attempted. It was well understood that the M3 design was deeply flawed, but the need for tanks was urgent.

The British ordered the M3 when they were refused permission to have their tank designs made by American factories. They were unhappy with the tall profile and had their own turret fitted—lower in profile with a bustle at the back for the radio set. Tanks modified with the new turret received the name "(General) Grant" while unaltered M3's were called "General Lee", or more usually just Grant and Lee. These names were, however, only used by British and Commonwealth forces; the U.S. Army never referred to the tanks as anything but M3 Mediums. The Grant required one fewer crew member than the Lee due to the movement of the radio to the turret. Nevertheless the M3 was successful as an interim solution and brought much needed firepower to British forces in the African desert.

The chassis and running gear of the M3 design was adapted by the Canadians to develop their Ram tank—a conventionally turreted tank. The hull was also used for self-propelled artillery and recovery vehicles.

The 3 inch Gun Motor Carriage T35 was the prototype of the M10. It had a 3 inch gun in a new sloped, circular, open topped turret, that was developed from the turret used on the Heavy Tank T1/M6, it was mounted on an early production Medium Tank M4A2 hull. The design may have been motivated by the success of the Soviet T-34, which it resembles in many ways including the similar armor thickness and slope and the choice of main gun.

The T35 was improved upon; it was given a sloped hull built on the M4A2 chassis, and had its circular turret replaced with a pentagonal turret, this model was designated the 3 inch Gun Motor Carriage T35E1. In June 1942 the 3 inch GMG T35E1 had its designation changed to become the 3 in Gun Motor Carriage M10, and ordered into full production.

A British variant, designated "Achilles", was developed to mount the successful 17-pounder anti-tank gun in a modified turret. It was used by the British, Canadian and Polish armies in Italy and north-west Europe.

Based on the A10 Cruiser tank, the Valentine was privately designed by the Vickers-Armstrong corporation (hence its lack of an "A" designation) and was submitted to the War Office in February 1938. The development team tried to combine the weight of a cruiser tank (so that suspension and transmission parts of the A10 could be used) with the armour of an infantry tank, which resulted in a very small vehicle with a cramped interior and two-man turret. Though its armour was still weaker than the Matilda's and, due to a weaker engine, it shared the same top speed, the new design was much less expensive and easy to produce.

The War Office was initially deterred by the size of the turret and the crew compartment. However, concerned by the situation in Europe, it finally approved the design in April 1939. The vehicle reached trials in May 1940, which coincided with the loss of nearly all of Britain's equipment during the evacuation at Dunkirk. The trials were successful and the vehicle was rushed into production as Infantry Tank III Valentine.

Several versions exist concerning the source of the name Valentine. The most popular one says that the design was presented to the War Office at St. Valentine's Day (February 14). Some sources, however, claim that the exact date the design was submitted was February 10. According to another version, the tank was called Valentine in honour of Sir John Valentine Carden, the man who led the development of the A10 and many other Vickers vehicles. Yet another version says that Valentine is an acronym for Vickers-Armstrong Ltd Elswick & (Newcastle-upon) Tyne.

The Valentine remained in production until April 1944, becoming Britain's most mass produced tank during the war with 6,855 units manufactured in the UK (by Vickers, Metropolitan-Cammell Carriage and Wagon and Birmingham Railway Carriage and Wagon) and further 1,420 in Canada. They were the Commonwealth's main export to the Soviet Union under the Lend-lease Act, with 2,394 of the British models being sent and 1,388 of the Canadian models, and the remaining 30 being kept for training.

The first Tetrarch prototype (then called a PR Tank or Purdah), was produced by Vickers-Armstrong in 1938. The vehicle was approved by the Army and production started in 1940, only to cease soon after following the bad performance of light tanks during the prevailing stage of the war.

The production of Mk VIIs was restarted in 1941 following the adoption of the vehicle by airborne forces, since it was light enough to be deployed from the air, via Hamilcar gliders, to support paratroops. The name "Tetrarch" was given to the vehicle in 1943.

The most interesting feature of the Tetrarch was its unique skid steering system that accomplished turns by the lateral movement of road wheels, which bowed the tracks. For sharp turns, the driver had to apply brakes to one track in the traditional fashion.

The Tetrarch turret design was also used on the Daimler Armoured Car.

The Tank, Light, Mk VIII, Harry Hopkins (A25) was developed by Vickers for airborne forces of the British Army during World War II. It was known as the Harry Hopkins tank, after the US politician.

The design was a further development of the Tetrarch light tank. It featured a new, redesigned turret and hull with thicker, sloping armour for improved shot deflection. Like the Tetrach, it had skid steering, which operated by bowing the tracks by lateral movements of the centre road wheels, but power assistance was added. The vehicle was armed with a QF 2 pounder gun, with 50 rounds of ammunition, and a coaxial 7.92 mm Besa machine gun, with 2,025 rounds of ammunition. A taper bore Littlejohn adaptor could be fitted to the barrel of the 2 pdr to use APCR shot which had improved armour penetration.

Three prototypes were authorised in April 1941 and production was then switched to Metro-Cammell, manufacturers of the Tetrarch. About 100 vehicles were eventually delivered, between June 1943 and March 1945, but it was not used in combat.