Cromwell's cooling system was a new design and put through over nine months of testing in a variety of configurations. This included the development of new fan drives and inlet louvres, which can be seen on the Cromwell engine deck. The resulting system for a Meteor-powered tank delivered both the necessary cooling performance, and reduced the power lost in driving the cooling system from 90 hp to 30 hp. This made the performance improvement of the Meteor over the Liberty even more pronounced and left room for expected development of the A27.