The Cromwell was the product of further development of British cruiser tanks designed to replace the Crusader. Powered by the new Rolls-Royce Meteor engine, a development of the Merlin, it had a top speed of 40mph. Armed with the powerful OQF 75mm gun, the Cromwell gave good service in the armoured regiments until the end of the war. The Sherman Firefly Vc was arguably the best combat version of the Sherman. Armed with the excellent 17 pdr gun it gave the British and Commonwealth armoured forces the ability to destroy even the heaviest German tanks. Originally built as a temporary alternative to the Challenger (an up-gunned Cromwell), it was so successful that it overtook the troubled Challenger design as the main British tank armed with the 17 pdr.