Question: When was the engine used in the Cromwell and Comet tanks discontinued?

full_context: Document 1: Cruiser Mk IV: The Cruiser tank Mk IV (A13 Mk II) was a British cruiser tank of the Second World War. It followed directly on from the Tank, Cruiser, Mk III (A13 Mk I). The first Mk IVs were Mk IIIs with extra armour fitted to the turret. Later Mk IVAs were built with the complete extra armour. The tank was used in France in 1940 and in the early part of the war in North Africa, before being withdrawn from service.
Document 2: Ordnance QF 2-pounder: The Ordnance QF 2-pounder (QF denoting "quick firing"), or simply "2 pounder gun", was a 40 mm British anti-tank and vehicle-mounted gun, employed in the Second World War. It was actively used in the Battle of France, and during the North Africa Campaign. As Axis tanks improved in armoured protection, it lost effectiveness, and it was gradually replaced by the 6-pounder, starting in 1942, though some remained in service until the end of the war. In its vehicle-mounted variant, the 2-pounder was also a common main gun on British tanks early in World War II, and was a typical main armament of armoured cars, such as the Daimler, throughout the war.
Document 3: Cromwell tank: The Cromwell tank, officially Tank, Cruiser, Mk VIII, Cromwell (A27M), was one of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War leader Oliver Cromwell, the Cromwell was the first tank put into service by the British to combine high speed from a powerful and reliable engine (the Rolls-Royce Meteor), and reasonable armour. However the originally proposed dual-purpose high velocity gun could not be fitted in the turret and the medium velocity dual purpose gun fitted proved inadequate. An improved version with a high velocity gun became the Comet tank.
Document 4: Mark V tank: The British Mark V tank was an upgraded version of the Mark IV tank. It was first deployed in 1918, used in action during the closing months of World War I, and in the Allied intervention in the Russian Civil War on the White Russian side, and by the Red Army, after they were captured. The tank was improved in several aspects, chiefly the new steering system and engine, but it fell short in other areas such as mechanical reliability and its insufficient ventilation. However, the Mark V was successful, especially given its limited service history, and primitive design.
Document 5: Rolls-Royce Limited: Rolls-Royce Limited owned a British luxury car and aero engine manufacturing business founded in 1904 by Charles Stewart Rolls and Frederick Henry Royce. Rolls-Royce Limited was incorporated on 15 March 1906 as a vehicle for their ownership of their Rolls-Royce business. Their business quickly developed a reputation for superior engineering quality and for manufacturing the "best car in the world", building on F H Royce's existing standing. Rolls-Royce became a leading manufacturer of piston aero-engines after it was brought into building them by the First World War.
Document 6: Rolls-Royce Meteor: The Rolls-Royce Meteor was a British tank engine developed in the Second World War. It was used in British tanks up to 1964.
Document 7: Comet (tank): The Comet tank or Tank, Cruiser, Comet I (A34) was a British cruiser tank that first saw use near the end of the Second World War. It was designed as an improvement on the earlier Cromwell tank, mounting the new 77 mm HV gun in a new lower profile and part-cast turret. This gun was effective against late war German tanks, including the Panther and, at most ranges, the Tiger. The tank was widely respected as one of the best British tanks of the war, and continued in service afterwards.
Document 8: Chieftain (tank): The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s, 1970s and 1980s. It was the "most formidable main battle tank in the world" at the time of its introduction in 1966 with the most powerful main gun and most effective armour of any tank yet made. . This was further improved while in service with Chobham armour upgrades.
Document 9: Rolls-Royce Holdings: Rolls-Royce Holdings plc is a British multinational public limited company incorporated in February 2011 that owns Rolls-Royce, a business established in 1904 and today designs, manufactures and distributes power systems for aviation and other industries. Rolls-Royce is the world’s second-largest maker of aircraft engines and has major businesses in the marine propulsion and energy sectors. All of its shares are tradeable on the London Stock Exchange and other markets.
Document 10: M3 Lee: The M3 Lee, officially Medium Tank, M3, was an American medium tank used during World War II. In Britain, the tank was called by two names based on the turret configuration and crew size. Tanks employing US pattern turrets were called the "Lee", named after Confederate general Robert E. Lee. Variants using British pattern turrets were known as "Grant," named after Union general Ulysses S. Grant.
Document 11: Medium Tank M7: The Medium Tank M7 was originally conceived as an up-gunned replacement for the Light Tank M3/M5. The project was supposed to mount the same 75mm armament as the M4 Sherman while retaining the light weight and maneuverability of the M3 Stuart; however, during development the weight of the prototype surpassed the US Army's standard for light tanks and crossed into the medium category and was renamed. The M7 had significantly less armor than the M4 Sherman, boasted no greater firepower, and held only a slight advantage in top speed. For these reasons, and because the M4 was already battle-tested and in full production, the M7 was put aside shortly after completing trials.
Document 12: Centurion (tank): The Centurion was the primary British main battle tank of the post-Second World War period. Introduced in 1945, it is widely considered to be one of the most successful post-war tank designs, remaining in production into the 1960s, and seeing combat in the front lines into the 1980s. The chassis was also adapted for several other roles, and these have remained in service to this day.
Document 13: Ram tank: The Tank, Cruiser, Ram was a cruiser tank designed and built by Canada in the Second World War, based on the U.S. M3 Medium tank. Due to standardization on the American Sherman tank for frontline units, it was used exclusively for training purposes and was never used in combat as a gun tank. The chassis was used for several other combat roles however, such as a flamethrower tank, observation post, and armoured personnel carrier.
Document 14: Cromwell Cup: The Cromwell Cup was the second ever football competition (after the Youdan Cup) and was held in Sheffield, England. It was held in February 1868 and named after Oliver Cromwell, manager of the local Alexandra Theatre (not the famous Lord Protector), who donated the cup. He also played for the Garrick club. The tournament was only open to teams under two years old. The final was held at Bramall Lane, Sheffield and was won by the world's first ever Golden Goal. The trophy is still held in the Sheffield Wednesday trophy cabinet.
Document 15: Rolls-Royce Silver Wraith: The Silver Wraith was the first post-war Rolls-Royce. It was made from 1946 to 1958 as only a chassis at Rolls-Royce's former Merlin engine plant, their Crewe factory, alongside the shorter Bentley Mark VI. The Bentley too was available as a chassis for coachbuilders but also for the first time could be bought with a Rolls-Royce built standard steel body.
ground_truth: 1964