Cromwell tank Tank , Cruiser , Mk VIII , Cromwell ( A27M ) , and the related Centaur ( A27L ) tank , were one of the most successful series of cruiser tank s fielded by Britain in the Second World War . The Cromwell tank , named after the English Civil War leader Oliver Cromwell , was the first tank put into service by the British to combine a dual - purpose gun , high speed from the powerful and reliable Meteor engine , and reasonable armour , in a balanced package . Its design formed the basis of the Comet tank . The Cromwell and Centaur differed in the engine used . While the Centaur had the Liberty engine of the predecessor cruiser tank , the Crusader ( and the interim A24 Cavalier ) , the Cromwell had the significantly more powerful Meteor . Apart from the engine and associated transmission differences , the two tanks were the same and many Centaurs were later fitted with the Meteor to make them Cromwells . The Cromwell first saw action in the Battle of Normandy in June 1944 . The tank equipped the armoured reconnaissance regiments of the Royal Armoured Corps , within the 7th , 11th and Guards Armoured Division s . While the armoured regiments of the latter two divisions were equipped with M4 Sherman s , the armoured regiments of the 7th Armoured Division were equipped with Cromwell tanks . The Centaurs were not used in combat except for those fitted with a 95mm howitzer , which were used in support of the Royal Marines during the invasion of Normandy . Development . Initial designs . Development of the Cromwell and Centaur dates to 1940 , as the Crusader tank was being readied for service . The General Staff was aware that the Crusader would become obsolete , and in late 1940 they set out the specifications for the new tank to replace it . The tank was to be fitted with the QF 6 pounder gun and was expected to enter service in 1942 . Vauxhall responded with the A23 , a scaled down version of their A22 Churchill infantry tank . This would have had 75 mm of frontal armour , used a 12 - cylinder Bedford engine , carried a crew of five and would have the same suspension as the A22 . Nuffield submitted the A24 , heavily based on its Crusader design and powered by its version of the Liberty engine , a V - 12 design dating the late days of World War I and now thoroughly outdated . Nevertheless , as the design was based on the Crusader , it was expected it could be put into production rapidly . The final entry was from Leyland and Birmingham Railway Carriage & Wagon ( BRC & W ) . Their design was similar to the Nuffield , but with different suspension and tracks . The designs were received and examined in January 1941 , with Nuffield ' s A24 being declared the winner on 17 January . Six prototypes of the Cromwell I were ordered for the spring of 1942 . These arrived four months late and by this time the design was already outdated . It was put into production anyway , but in service it proved entirely underpowered and only a small number were built . Delays in the A24 program led to demands to get the QF 6 pounder into service earlier . This led to a series of up - gunned Crusaders mounting the 6 - pounder . A27 . With the start of the war , Rolls - Royce ended car production and set up a design team looking for other ways to use their production capacity . The team formed under the direction of Roy Robotham at Clan Foundry near Belper , north of Derby . In October 1940 Robotham met with Henry Spurrier of Leyland Motors to discuss British tank design . They decided to attempt to fit a Rolls - Royce Merlin engine to a Leyland tank for testing . They removed the supercharger from a Merlin Mk . III and fitted it to a Leyland - built Crusader . Delivered to Aldershot on 6 April 1941 , the test team had trouble timing its runs because it was so fast , estimating it reached . Everyone was so impressed by this display that Leyland arranged to start production of 1 , 000 examples of the engine as the Meteor . They planned to fit this to BRC & W - built versions of their original A24 submission . However , in mid - 1941 , Leyland changed its mind , concerned about cooling problems . They instead suggested using a diesel engine of their own design , although this would produce only compared to over 500 from the Rolls design . The Tank Board then placed an order directly with Rolls for the Meteor . The resulting design was ordered as the A27 . When Leyland suggested that the tank be designed to fit either the Meteor or the Liberty , the two versions were given the General staff numbers A27M and A27L , respectively , and the names Cromwell III and Cromwell II . The diesel concept was abandoned . The first prototype of a Meteor - powered Cromwell III was delivered in January 1942 , several months before the A24 that was supposed to precede it . With nearly it proved to be exceptionally mobile when tested . Orders were placed for both versions , as there were concerns about the production rate of the Meteor . Even when assigned reduced production quotas , BRC & W proved unable to meet demand , and Leyland eventually took over production of both versions . Rover enters . Rolls was at this time having trouble meeting demand for the Merlin , let alone the Meteor . Meanwhile , Rover was having troubles developing Frank Whittle ' s Power Jets W . 2 jet engine design due to increasing animosity between the engineers at Power Jets and Rover . Things became particularly heated when Whittle learned that Rover had set up a secret lab to develop their own versions of the design . Whittle had , during the same period , contacted Rolls for help delivering some of the required parts that Rover proved unable to produce . A solution to both their problems was offered by Ernest Hives , a Rolls board member , who had met Whittle and was fascinated by the jet engine . Hives called a meeting with his counterpart at Rover , Spencer Wilks , and the two met late in 1942 at the Swan and Royal pub in Clitheroe . Hives offered to trade the Meteor for the W . 2 , an offer Wilks jumped at . The official handover took place on 1 January 1943 . Rover set up production at their Tyseley factory , and an additional line was set up by Morris Motors in Coventry . Production began in November 1942 . That month , new names were given to all three designs ; the original A24 Cromwell I became the Cavalier , the Liberty powered A27L Cromwell II became Centaur , and the Meteor powered A27M kept the name Cromwell . It would take considerable time for Rover to make ready production lines for the Meteor , and it was not until a few months later , in January 1943 , that sufficient Meteor engines were available and the A27M Cromwell began production . The Centaur production design allowed for the later conversion to the Meteor engine and many Centaurs were converted to Cromwells before use . Final changes . The first real field test of the design was carried out in August – September 1943 , when examples of the Centaur , Cromwell , Sherman M4A2 ( diesel engine ) and Sherman M4A4 ( multi - bank petrol engine ) were all tested in Exercise Dracula , a 2 , 000 mile long trip around Britain . The Shermans proved to be the most reliable , by far , requiring 420 hours of specialist fitter attention over a total distance travelled of . This corresponds to 0 . 03 hours per mile . In comparison , the Cromwells drove and required 814 hours , or 0 . 07 hours per mile . The Centaur managed only due to constant breakdown , and required 742 hours , or 0 . 087 hours per mile . The Cromwell and Centaur were given additional time to work out these problems . The Cromwell ' s problems were mostly related to oil leaks and brake and clutch failures , an observer noted that these were well known and should have been corrected before this point . The crews , however , expressed their love for the design , and especially its speed and handling . The Centaur was largely dismissed , with one observer expressing his hope that units were being equipped with it only for training purposes . The same reviewers unanimously supported the Sherman . A similar test in November demonstrated the Cromwell was improving , while the underpowered Centaur faired no better than the first test . The production model design was finalized on 2 February 1944 when Leyland released specifications for what they called the " Battle Cromwell " . This included a number of minor changes to the basic design , including of extra armor below the crew compartment , seam welding all the joints to waterproof and strengthen the tank , and standardizing on the Meteor engine and Merritt Brown transmission . Production . Total A27 production consisted of 4 , 016 tanks , 950 of which were Centaurs and 3 , 066 Cromwells . In addition , 375 Centaur hulls were built to be fitted with an anti - aircraft gun turret ; only 95 of these were completed . Design . The frame was of riveted construction , though welding was used later . The armour plate was then bolted to the frame ; large bosses on the outside of the plate were used on the turret . Several British firms besides Leyland contributed to production of the Cromwell and Centaur , including LMS Railway , Morris Motors , Metro - Cammell , Birmingham Railway Carriage and Wagon Company and English Electric . Some variants were produced with tracks ; later , 15 . 5 - inch tracks were used . The suspension was of the Christie type , with long helical springs ( in tension ) angled back to keep the hull sides low . Of the five road wheels each side , four had shock absorbers . The tracks were driven by sprocketed wheels at the rear and tension adjusted at the front idler , this being standard British practice . As with previous Christie - suspension cruiser tanks , there were no track return rollers , the track being supported instead on the tops of the road wheels . The side of the hull was made up of two spaced plates , the suspension units between them , and the outer plate having cutouts for the movement of the road - wheel axles . The gearbox had five forward and one reverse gears . The first gear was for " confined spaces , on steep inclines or . . . sharp turns " . The Meteor engine delivered 540 hp at 2 , 250 rpm . This was the maximum rpm , which was limited by governors built into the magnetos . Fuel consumption on " pool " petrol ( 67 octane ) was between 0 . 5 and 1 . 5 miles per gallon depending on terrain . The driver sat on the right in the front of the hull , separated from the hull gunner by a bulkhead . The driver had two periscopes and a visor in the hull front . The visor could be opened fully or a small " gate " in it opened ; in the latter case a thick glass block protected the driver . A bulkhead with access holes separated the driver and hull gunner from the fighting compartment . A further bulkhead separated the fighting compartment from the engine and transmission bay . The engine compartment drew cooling air in through the top of each side and the roof and exhausted it to the rear . To allow fording through up to deep water , a flap could be moved to cover the lowermost air outlet . Air for the engine could be drawn from the fighting compartment or the exterior ; it was then passed through oil bath cleaners . The Cromwell had revisions to make before service , changing from the QF 6 - pounder ( 57 mm ) to the ROQF 75 mm gun , which was an adaptation of the 6 - pounder design to fire the ammunition of the US M3 75 mm gun , which gave it a better HE round to use in infantry support . This meant that the 75 mm used the same mounting as the 6 pounder . In June 1944 , the Cromwell saw action during Operation Overlord , the Allied invasion of Normandy . It had a mixed reception by crews , being faster , with a lower profile than the Sherman tank and thicker frontal armour plate as against the on the glacis of the early Shermans , though it was unsloped and hence less effective . On later Cromwells this was increased , first to , then to . The 75 mm gun , though able to fire a useful HE shell , was not as effective against armour as the 6 - pounder or the Ordnance QF 17 pounder gun . A derivative of the Cromwell , the Cruiser Mk VIII Challenger , was built to take the 17 - pounder ; but only a small number were built . Most 17 - pounder armed tanks to see service in the war were the Sherman Firefly variant of the Sherman . There was a 7 . 92 mm Besa machine gun mounted co - axially to the main armament , operated by the gunner . A second was " gimbal " mounted in the front of the hull . The mounting gave 45 degrees of coverage to the front ( it had 25 degrees of vertical movement as well ) and sighting was by a No . 35 telescope , which was connected through a linkage to the mounting . In the top of the turret was a 2 inch " bombthrower " angled to fire forward and thirty smoke grenade s were carried for it . Performance . The Cromwell was the fastest British tank to serve in the Second World War , with a top ( ungoverned ) speed of . However , this speed proved too much for even the Christie suspension and the engine was governed to give a top speed of , which was still fast for its time . Thanks to its excellent engine power and Christie parentage the Cromwell was very agile on the battlefield . The dual purpose 75 mm main gun fired the same ammunition as the US 75 mm gun and therefore it had around the same HE and armour - piercing capabilities as the 75 mm equipped Sherman tank . The armour on the Cromwell ranged from 8 mm up to 76 mm thick overall . However , on all - welded vehicles built by BRCW Co . Ltd , the weight saved by the welding allowed for the fitting of appliqué armour plates on the nose , vertical drivers ' plate and turret front , increasing the maximum thickness to 102 mm . These vehicles are identified by their War Department numbers carrying the suffix W , e . g . T121710W . This armour compared well with that of the Sherman , although the Cromwell did not share the Sherman ’ s sloped glacis plate . The Cromwell crews in North - West Europe succeeded in outflanking the heavier and more sluggish German tanks with superior speed , manoeuvrability and reliability . However , the Cromwell was still not a match for the best German armour and British tank design would go through another stage , the interim Comet tank , before going ahead in the tank development race with the Centurion tank . Combat service . The Centaur was chiefly used for training ; only those in specialist roles saw action . The Close Support version of the Centaur with a 95 mm howitzer saw service in small numbers as part of the Royal Marine Armoured Support Group on D - Day and a number were used as the chassis for combat engineering vehicles , such as an armoured bulldozer . The Sherman remained the most common tank in British and other Commonwealth armoured units in Europe . Cromwells were used as the main tank in the armoured brigades of only the 7th Armoured Division , although the Cromwell was used in the armoured reconnaissance regiments of the other British armoured divisions ( Guards Armoured Division and 11th Armoured Division ) in North - west Europe , because of its speed and relatively low profile . The Cromwell , in turn , was succeeded by small numbers of the Comet tank , which was similar to the Cromwell , being based on it and shared some components but had a superior gun in the 77 mm gun ( a version of the 17 pounder with different ammunition ) . The Cromwell was found to be very reliable with excellent speed and manoeuvrability , though it required more maintenance than the Sherman . It was modified so that the exhaust fumes were redirected so that they were not drawn into the fighting compartment , a problem found when tanks were drawn up together , preparing to advance . In northern Europe , the Cromwell was used by Allied units of the 1st Polish Armoured Division ( 10th Mounted Rifle Regiment ) and 1st Czechoslovak Armoured Brigade . After the war , the Cromwell remained in British service , and saw service in the Korean War with 7 RTR and the 8th King ' s Royal Irish Hussars . The Cromwell / Centaur had the distinction of being the first tank to go into service with the Greek Army during the re - formation following the Second World War . Fifty - two Centaur I tanks were donated early in 1946 , during the opening stages of the Greek Civil War but they were kept in storage due to the lack of trained personnel . In 1947 , the first Greek officers returned from training courses in the United Kingdom and training of tank crews began . The Centaur saw limited service in the civil war as in 1949 battles were fought on mountains . Centaurs formed the core of the Greek Armour Corps during the 1950s and were retired in 1962 , having been replaced by US - built M47s . Finland used the Charioteer version of the Cromwell post war . Variants . The modifications and developments of the Cromwell were classified under " Type " and " Mark " . A single Mark could cover up to four Types and a Type up to six Marks making classification complex . The Types ran from A ( the earliest Cavaliers , Centaurs and Cromwells ) to F ( a late model Cromwell with driver ' s side escape hatch ) . Surviving vehicles . Around 56 Centaur and Cromwell tanks survive , ranging from scrapyard wrecks to fully restored museum vehicles . Cromwell tanks . Around 26 Cromwell tanks exist in various states . Centaur tanks . Around 17 Centaurs and 9 Centaur Dozers exist in various states . Other examples include :