They're fast, rare and boast huge spoilers - the Ford Sierra RS Cosworth and the Ford Escort RS Cosworth. Two ordinary family car models were transformed into lean, mean driving machines that gave purebred race cars a run for their money. Christian Gratl, son of a race car driver, shows us what the Cosworths can do. For more go to http://www.dw.de/drive-it-the-motor-magazine-2012-12-05/e-16375193-9798