Before it can go into series production, the new edition of the sports sedan must first complete a programme of testing whose breadth and intensity far exceed the stresses and strains of everyday driving. There could be few greater contrasts with the hot-weather testing in the USA than what goes on at the BMW Group’s winter testing centre not far from the Arctic Circle. Arjeplog in Sweden offers the perfect conditions for a testing programme that eclipses anything day-to-day driving in central Europe, North America or Asia can throw at a car. However, Arjeplog doesn’t only give the prototypes the chance to demonstrate their imperviousness to extreme cold – it also provides the stage for the new model’s chassis controls systems to show off their full range of abilities. The closed-off expanses of ice offered by Lake Kakel and the “Mellanström-Runde”, one of the most popular test routes around Arjeplog, couldn’t be better suited for fine-tuning the DSC stability system and its myriad functions. Indeed, on this glassy surface you don’t need to drive quickly to provoke the control systems into action and therefore analyse their responses. All of which allows the link-up between DSC and the xDrive all-wheel-drive system and the interplay with the new BMW 3 Series Sedan’s M Sport differential to be refined down to the last detail under constant conditions.