FV4401 Contentious FV 4401 " Contentious " was a prototype British air - portable tank destroyer of the early 1960s . At least one prototype was constructed and tested , although no production vehicles were built or saw service . Project " Prodigal " . The vehicle was developed as part of " Project Prodigal " , as research into future armoured fighting vehicle s . " Prodigal " would eventually give rise to the CVR ( T ) series of British light tanks and related vehicles . The intention here was to produce an air - portable tank destroyer . The vehicle ' s role was for a flexible strategic response to conflicts around the last vestiges of Empire . Despite the low intensity of such conflicts , it was assumed that the increasing supply of Soviet T - 54 tanks to satellite state s would require an anti - tank capability greater than previous light tank s . This was " not " seen as a substitute for a main battle tank ; one which would have to be heavily armed to deal with the massed and heavily armoured Soviet tanks of the Cold War . In particular , there was no attempt made at protection against the NBC threat that was expected for any European conflict . " Contentious " . This required a particularly lightweight vehicle , which restricted the possibility of a conventional tank with a conventional turret . The path chosen was that of a low - profile open hull with a semi - fixed gun , similar to the layout of the wartime Alecto . This small hull necessitated a small crew , of only two , which in turn required an autoloader , particularly for the heavy armament and ammunition in mind . The gun chosen was the QF 20 pounder ( 84 mm ) , already in use in the Centurion tank , although now fitted with an autoloader . The mount was fixed in elevation and had only a limited traverse . Most aiming relied on steering the entire tank on its tracks . Elevation used an unusual system , a hydraulic suspension system with independent height control of each wheel station . This allowed the entire tank chassis to be tilted back and forth . This system had already been demonstrated in the Swedish S - tank . The chassis components were based on those of the Comet tank , although with only four roadwheels rather than the Comet ' s five . The prototype was completed and tested on the firing ranges of Kirkcudbright Training Area . This was only a boilerplate example : it was not only unarmoured , but the armour layout design had not been completed and the actual body of relatively high and vertical plates is unlikely to have been the shape , let alone the material , used for a final example . In particular , the petrol tanks were exposed and mounted above the track guards . The vehicle was also tested at Lulworth , in tests against a wheeled vehicle to test the virtues of both tracked and wheel arrangements for the " Prodigal " air - portable tank destroyer . The vehicle chosen was the " Rhino " , a six - wheeled skid - steered experimental chassis , powered by a Rolls - Royce Meteorite engine . Drivers were instructed to drive in pursuit of targets , both fixed and moving , and to attempt to track them with a simple windscreen - mounted sight . The " Rhino " ' s steering was infamously difficult to control precisely and it was found that the tracked Contentious performed better . As with the Centurion , Contentious was later up - gunned . Although first tested with the 84 mm 20 pounder , the Bovington example later gained a L7 105 mm gun , a derivative of the 20 pounder . The replacement was relatively easy , as the 105 mm is largely a rebarrelled version of the 84mm and has a similar breech . Photographs of the prototype do show some change to the recoil cylinders between the two . Twin recoilless design . A further design for the " Prodigal " requirement used a pair of the 120 mm recoilless rifle s , as used for the WOMBAT , and fitted with seven - round revolver autoloaders . These were mounted on a swivelling mounting above a low boat - shaped hull with conventional suspension , crewed by a single commander / driver / gunner . The mounting could elevate conventionally . The autoloaders and their ammunition were carried in armoured boxes above the hull , with the reaction nozzles of the recoilless rifle protruding behind . Sighting for these recoilless rifles was to be the same M8C . 50 spotting rifle s , one for each barrel , as used with the WOMBAT .