In order to accommodate the large weapon and a second loader, a turret larger than that of the Cromwell was required and as such the hull had to be enlarged. It was lengthened and an extra road wheel added. As a consequence of the weight increase, the armour had to be reduced and the hull machine gun was removed for stowage of the long 17pdr cartridges.
Unfortunately, due to some short sightedness no provision had been made for deep wading trunking and thus the A30 was unavailable to participate in the Normandy landings, the tank having to wait until ports had been secured and the Mulberry harbours completed. The Challenger, despite its high centre of gravity was liked by its crews as it was somewhat faster and more agile than the equivalently armed Sherman Firefly. The Firefly design which had been a backup strategy proved to be easier to build and production of the Challenger was stopped with about 200 units built. Many of the A30s were issued to units using the Cromwell to ease maintenance logistics, as they shared many of the same parts.
The Avenger or to give its full designation SP 17pdr, A30 (Avenger) was a variant on the Challenger idea with a differently shaped open topped turret to help reduce weight. With priority production at Vauxhall Motors for the Comet tank, those built in 1945 were not ready for use until after the end of the war in Europe. Some 250 were built and these formed part of the BAOR in Germany.