Caterham is launching a road-legal version of the car it uses on its driving experience days . The CDX Limited Edition Seven comes with a roll-bar, a limited-slip diff and runs on sticky Avon rubber to improve its ability on the track.Like the Caterham Academy race cars, the CDX Limited Edition Seven is powered by the 1.6-litre, K-series four-cylinder unit, which is tweaked to produce 135bhp instead of 120bhp. The roll cage is the same one used by the driving experience cars and shared with the Superlight, while suspension is standard. The CDX Limited Edition Seven costs from £17,495 in component form. If you want a factory-built one, you’ll need to find £20,495.