By then, Ali had begun his comeback. But it was not until 1974 that he finally regained his WBA crown, defeating Foreman in the ‘Rumble in the Jungle’. He remained champion for four more years, retiring for the first time in 1979 and for good in 1981.

It is an inspiring story, and it has undoubtedly provided inspiration for a lot of African Americans - and not just boxers, either - in the years since Ali began to suffer from the Parkinson’s Disease that was first diagnosed in the eighties. But Mann was less concerned with the inspiration than with the man who provided it. “I wasn’t interested in telling this story as a docudrama or an idealisation of Ali,” he insists. “To idealise Ali is to diminish his humanity. It would rob him of the inconsistencies and errors that make us who we are, as well as the true courage and commitment to excel as a man and an athlete.

Mann with ‘the Man’ - the Ali director on set with Jeffrey Wright, Ross Haines, Mykelti Williamson, Jamie Foxx, Will Smith, Jon Voight, Ron Silver and Charles Shufford.

“It’s an awesome task to try to take on Ali,” he adds. “But it’s also very exciting, which is why Will and I wanted to do it. You do it because it gets your blood running, because you love the material. You love the man. You love what the man represents - today and 30 years ago.”

US audiences seem to have responded to the approach, making Ali the biggest Christmas Day opener in the history of Hollywood, “scoring a first-round knock-down”, according to Columbia distribution chief Jeff Blake.

But perhaps the overall impact of the film - and of the man - is best described by Nona Gaye, who plays the Champ’s second wife, Belinda, in the film. Gaye knows all about fame (she is the daughter of soul legend Marvin Gaye) and she had met the real-life Ali long before going on the set of Mann’s film.

“He’s more than a sports hero,” she says. “He transcended that just in the way he affects everybody. You hear him talk, and you’re captivated. I first met him as a little girl with my father, and when I saw him again after I’d gotten this part, he leaned over and whispered in my ear, ‘You look just like your daddy.’ I got all girlie and silly. He’s just got that charisma. He always had a fire and a passion for what he did. You could tell how much he wanted to win, how confident he was that he was going to win. He understood something. He just knew.”