The Challenger 2 is the first British Army tank since World War II to be designed, developed and produced exclusively by a single prime contractor, Vickers Defence Systems, with set reliability goals laid down in the fixed price contract. The hull and automotive parts of the Challenger 2 are based upon its predecessor Challenger 1, but Challenger 2 incorporates over 150 improvements aimed at increasing reliability and maintainability. The turret of Challenger 2 is a totally new design. Armour is an uprated version of Challenger 1's Chobham armour.