When was the engine used in the Cromwell and Comet tanks discontinued?
Cromwell tank:  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. Rolls-Royce Meteor: The Rolls-Royce Meteor was a British tank engine developed in the Second World War.
i don't know