Archie Scott Brown was seriously handicapped from birth. However, he was a terrific racing driver. He won 71 races, 15 of which international competitions. He managed to participate in the 1956 British GP, although he was impeded to have a real F1 career, since he could not have the required international licence.
Alan Stacey had his right leg cut just below the knee and raced with a prosthetic leg (and his mechanic did not have an arm!). He managed to become an official Lotus F1 driver.
Does anyone know any other drivers who made it to the top even though they had serious handicaps?
