It’s difficult to find a precise word to describe his slow, loping walk. Not a strut, not a swagger…nothing defiled by conceit. And yet that gait, set moving as if by some inner lode of burning coal, has traversed over half-century of Indian cinema. And, at age 80, he’s still walking. Amitabh Bachchan, the man, may be different from Amitabh Bachchan, the actor… but a ceaseless quest defines them both. Here we chart that journey in a scene-by-scene biography. From his birth during the Quit India days, his early life, a couple of mundane desk jobs, and his struggling years when auteurs willing to bet on him were rare. Then the Seventies, when he lit up Hindi cinema like dynamite from a burning beedi. His misadventures in politics and business.…