The Audi Quattro was the car which changed rallying forever - the first rally car to successfully employ four wheel drive and among the pioneers of turbocharging. The success of the Quattro and the introduction of Group B in 1982 rendered more conventional cars such as the Ford Escort and Opel Manta almost obsolete overnight and led to an "arms race" the like of which motor sport has never seen. Manufacturers including Ford, Peugeot, Austin Rover, Renault and Citroen all built cars to compete in Group B but it was the cars of Audi and Lancia which have become the most iconic. Originally a production-based 300bhp coupe, Audi's Quattro morphed over five years into the short wheel base 5 cylinder, 600bhp S1 seen here, charging through the Alps during the 1986 Monte Carlo Rally in the hands of Hannu Mikkola who drove for the works team throughout the Group B era. He is chased by Henri Toivonen's victorious Lancia Delta S4, a car so specialised that it shared little other than the name with the production Delta and the Group A Integrale which followed. The S4 was a tubular space framed supercar with a mid-mounted, 1800cc engine, supercharged and turbo charged with four wheel drive. It was perhaps the ultimate evolution of the Group B car and Toivonen's artistry behind the wheel made him a firm favourite with crowds wherever he went. The popularity of Group B - and the extreme nature of the cars it produced - contributed to its downfall, with several high profile fatal accidents, including some involving spectators. The deaths of Toivonen and co-driver Sergio Cresto during the Tour de Corse later the same season were almost the last straw. At the end of 1986 Group B cars were outlawed and arguably rallying's most glorious era drew to a close.