Like naval cruisers, cruiser tanks were fast and mobile for operations independent from slower-moving infantry with their heavier infantry tanks and artillery.
When gaps had been forced through the opponent's front by the infantry tanks, cruisers were to penetrate to the rear and attack lines of supply and communication centres in accordance with the theories of J.F.C. Fuller, Percy Hobart and B. H. Liddell Hart.
The cruiser tank was designed for use in a manner similar to cavalry, which made speed the most important factor and to achieve this, early cruisers were lightly armoured and armed to save weight.

The emphasis on speed unbalanced the British designs; on limited engine power, the speed was possible only by sacrificing armour protection (by comparison infantry tanks operating at soldiers' pace could carry far more armour).
The idea that "speed is armour" was considered most important in the Royal Tank Corps.
It was not realised that the principle of mobility was a liability against the German policy of accepting lower speeds for superior armour and armament, ensuring that even one round from a German medium tank could easily destroy a cruiser.

An even bigger problem for most cruiser tanks was the small calibre of their main gun.
The first cruisers were armed with the 2-pounder (40 mm) gun.
This gun had adequate armour penetration against early war tanks, but was never issued high explosive ammunition.
This made the cruisers less able to deal with towed anti-tank guns, which became a major issue with the extended combat ranges of the Desert Campaign.
the additional machine gun turret (as mounted on the Crusader) was no substitute for HE rounds.
As the armour of German tanks increased British cruisers were up-gunned with the more powerful 57 mm QF 6-pounder gun, starting with the Crusader Mk.
III (an interim move pending the introduction of the next cruiser tank).
Early marques of what would become the Cromwell were also fitted with the 6-pdr but this gun still did not have a satisfactory HE round.
The Cromwell as planned was to have a High Velocity 75 mm gun but the design was not sufficient to mount one and so  decided that the new Cromwell tanks would be fitted with the QF 75mm (a bored out 6-pdr design that could take US 75 mm ammunition).
The new 75 mm gun providing greater HE capability at the expense of some armour penetration, however it was still adequate to deal with the majority of German armoured vehicles.
Part of the Cromwell's success was its high-power to weight ratio, provided by the adoption of the Rolls Royce Merlin engine as the Meteor, which delivered sufficient power for the Cromwell to have a maximum speed around 40 mph (64 km/h) on roads.
The new powerplant enabled the tank to be far more heavily armoured and armed than previous cruiser designs.

As the Cromwell could not be fitted with the HV 75 mm, work was undertaken to produce a tank for the powerful 17-pdr anti-tank gun, able to take out the heaviest of German vehicles.
To this end the Cruiser Mk VIII Challenger was developed, mounting a 17-pdr gun on a lengthened Cromwell hull and a totally new turret.
The Challenger was an unhappy compromise, though it was popular with its crews the cut in armour protection to allow the mounting of the larger gun meant it was not well suited to closer range engagements and it threw its tracks more often than the Cromwell.
As the UK had large numbers of US M4 Sherman tanks, an extemporaneous conversion of the Sherman to take a 17-pounder (as the Sherman Firefly) proved effective in providing more 17-pounder gun tanks, the Firefly accompanied Churchills, Shermans and Cromwells generally at a ratio of 1:4.
The production of Fireflies greatly outpaced that of the Challenger but in Cromwell-equipped units, the Challenger was generally preferred as the Sherman had a slower road speed and inferior cross-country mobility.

The culmination of British efforts was the Comet tank with a cut down 17-pounder design, the 77 mm HV.
The Comet was a further development of the Cromwell, a "heavy" cruiser tank, which sought
Like naval cruisers, cruiser tanks were fast and mobile for operations independent from slower-moving infantry with their heavier infantry tanks and artillery. When gaps had been forced through the opponent's front by the infantry tanks, cruisers were to penetrate to the rear and attack lines of supply and communication centres in accordance with the theories of J.F.C. Fuller, Percy Hobart and B. H. Liddell Hart. The cruiser tank was designed for use in a manner similar to cavalry, which made speed the most important factor and to achieve this, early cruisers were lightly armoured and armed to save weight.
The emphasis on speed unbalanced the British designs; on limited engine power, the speed was possible only by sacrificing armour protection (by comparison infantry tanks operating at soldiers' pace could carry far more armour). The idea that "speed is armour" was considered most important in the Royal Tank Corps. It was not realised that the principle of mobility was a liability against the German policy of accepting lower speeds for superior armour and armament, ensuring that even one round from a German medium tank could easily destroy a cruiser.
An even bigger problem for most cruiser tanks was the small calibre of their main gun. The first cruisers were armed with the 2-pounder (40 mm) gun. This gun had adequate armour penetration against early war tanks, but was never issued high explosive ammunition. This made the cruisers less able to deal with towed anti-tank guns, which became a major issue with the extended combat ranges of the Desert Campaign. the additional machine gun turret (as mounted on the Crusader) was no substitute for HE rounds. As the armour of German tanks increased British cruisers were up-gunned with the more powerful 57 mm QF 6-pounder gun, starting with the Crusader Mk. III (an interim move pending the introduction of the next cruiser tank). Early marques of what would become the Cromwell were also fitted with the 6-pdr but this gun still did not have a satisfactory HE round. The Cromwell as planned was to have a High Velocity 75 mm gun but the design was not sufficient to mount one and so  decided that the new Cromwell tanks would be fitted with the QF 75mm (a bored out 6-pdr design that could take US 75 mm ammunition). The new 75 mm gun providing greater HE capability at the expense of some armour penetration, however it was still adequate to deal with the majority of German armoured vehicles. Part of the Cromwell's success was its high-power to weight ratio, provided by the adoption of the Rolls Royce Merlin engine as the Meteor, which delivered sufficient power for the Cromwell to have a maximum speed around 40 mph (64 km/h) on roads. The new powerplant enabled the tank to be far more heavily armoured and armed than previous cruiser designs.
As the Cromwell could not be fitted with the HV 75 mm, work was undertaken to produce a tank for the powerful 17-pdr anti-tank gun, able to take out the heaviest of German vehicles. To this end the Cruiser Mk VIII Challenger was developed, mounting a 17-pdr gun on a lengthened Cromwell hull and a totally new turret. The Challenger was an unhappy compromise, though it was popular with its crews the cut in armour protection to allow the mounting of the larger gun meant it was not well suited to closer range engagements and it threw its tracks more often than the Cromwell. As the UK had large numbers of US M4 Sherman tanks, an extemporaneous conversion of the Sherman to take a 17-pounder (as the Sherman Firefly) proved effective in providing more 17-pounder gun tanks, the Firefly accompanied Churchills, Shermans and Cromwells generally at a ratio of 1:4. The production of Fireflies greatly outpaced that of the Challenger but in Cromwell-equipped units, the Challenger was generally preferred as the Sherman had a slower road speed and inferior cross-country mobility.
The culmination of British efforts was the Comet tank with a cut down 17-pounder design, the 77 mm HV. The Comet was a further development of the Cromwell, a "heavy" cruiser tank, which sought 
Cruiser tank