He's played presidents, professors, doctors and judges. He was God in Evan Almighty and Nelson Mandela in Invictus. Yet Morgan Freeman is the first to admit he's not so special in real life. "The only thing I've ever been really good at, if I can toot my own horn here, is pretending to be something I'm not," he says, modestly, in that rich, comforting baritone - one of the reasons he's so frequently cast as the voice of authority.
His latest film, Lucy, begins with Freeman's character, neurology expert Professor Norman, explaining the human brain - espousing the commonly held theory that we only use 10 per cent of the organ. "I subscribe to it because it's hopeful to subscribe to it; that at some point or other we may access more of the brain," he tells me. "But on the other hand, that might not be the truth. The truth may be that we use quite a bit more of the brain than 10 per cent of it."
Arguably, you may not need to use much more than the requisite 10 per cent to follow Lucy, a typically frenetic action film from Luc Besson, the French director behind The Fifth Element, Léon: The Professional and La Femme Nikita. The story sees Scarlett Johansson play the title character, an exchange student in Taipei who becomes a drug mule for gangsters peddling an experimental narcotic. When it leaks into her stomach, it expands her brain capacity to superhuman levels.
It's not the first time Freeman has worked with Besson. In 2005, they made Unleashed, a crime drama co-starring Jet Li Lianjie, which Besson wrote but didn't direct. "I met him [Besson] then and I liked him a lot. And the moviemaking experience just made me like him more. He's really terrific and very easy to work with," the actor says.
Given that Unleashed arrived in the year he won his only Oscar to date - for Clint Eastwood's boxing saga Million Dollar Baby - it's been understandably overlooked. Still, this little passage symbolises Freeman's career, which is a mix of high and low art.
Quite how he can switch from the majesty of Eastwood's 1992 revisionist western Unforgiven and Frank Darabont's beloved prison saga The Shawshank Redemption to throwaway action offerings such as Wanted and Olympus Has Fallen is anyone's guess.
This year alone, he's voiced a blind sage in The Lego Movie, played a government scientist in sci-fi mystery-thriller Transcendence and will soon be seen reprising his role as Dr Cameron McCarthy, yet another expert, in Dolphin Tale 2.
Now 77, his hair bright silver, it almost seems rude to mention the idea of retirement; he still loves acting, after all. "As much as ever," he says. "I guess I qualify as an old hand now." The only thing you won't find him doing is directing. He tried it once, on 1993's Bopha! - the tale of a black policeman during the apartheid regime in South Africa - but it wasn't enough to make him return for a second visit. "It's not my first calling. It's not something I'm really dying to do," he says.
Freeman may not purport to be an expert in much beyond acting but working on Lucy has clearly given him food for thought. "What about all the stuff that we're not aware of? We're not aware of breathing. But all of that is part of all of our life functions. It has to have something to do with the brain. That's a thought! But we have to remember that the brain suggests learning. A spider is not taught how to make a web. It's hatched knowing. A bird is not taught how to make a nest."
And a Freeman was not taught how to act? "Maybe. Maybe not," he says with a grin. "I may just be like a spider. It's innate." True or otherwise, he started acting when he was nine years old. Born in Memphis, Tennessee, the son of a teacher and a barber, he won a drama competition at the age of 12 and, while still at school, performed in a Nashville radio show. After serving in the US Air Force for four years, he took acting lessons at the Pasadena Playhouse before beginning a career in theatre.
While it took some years for him to establish his film credentials - his Oscar-nominated supporting part as a pimp in 1987's Street Smart and his second of five Oscar nods for his role as a chauffeur in 1989's Driving Miss Daisy, did the trick - he didn't see himself as a flop. "My success started for me when I got my first professional job on a New York stage. I was successful. I'd arrived. I thought, 'From now on, it's just one step at a time. Keep working.' My aim from childhood was to be a movie actor. I'd always wanted to do that, and I was extremely happy and content that I had a career in film, wherever I was."
Neither does he see it as strange that success came to him relatively late in life. "You have your life as a map: either you mapped it out, or providence mapped it out, or you mapped it together. It's unfortunate if it's only providence - you have no say in it. But I think you do have something to say, because you're making choices as you go along.
"I accept that that was the path that I was supposed to take, if I was to survive my own life, my own abilities and shortcomings."
Twice married and divorced, Freeman has four children - including Alfonso Freeman, who is also an actor. Was he worried about his son getting into the business? "No, not at all. Not worried about him getting into the business. But I was worried about the fact that he may not succeed. It's not easy to follow in your father's footsteps, particularly if he gets a high profile."
Did he cope? "Well, I don't know about that. I try to tell him 'Don't worry about it. Don't try to be a star. Just try to be a working actor.'"
Talking to Freeman, you get the impression that he'd like to be just that. He says there's "a barely acceptable downside" to fame.
"There's no such thing as privacy and yet all you look for is privacy. I don't want to be seen in public. I dislike travelling because I gotta walk through airports. I cringe when someone says 'Hey, Morgan Freeman!' I want to run when someone approaches me with a piece of paper and pencil, particularly in crowded situations. They're never going to understand you when you say, 'No I don't do that.'"
Maybe this quest for privacy is why Freeman, when he was 65, earned a private pilot's licence - following in the footsteps of Harrison Ford, John Travolta and Tom Cruise. "It's not much different than driving a car," he says. "A little more complicated when you're landing."
Sadly, he had to give up flying in 2008 after sustaining injuries from a serious car accident. "I was so proud of myself for having got my licence," he says. "And by the time I got hurt, I was flying jets." Perhaps he is good at more than he gives himself credit for.
Lucy opens on August 7