The actor, who stars as the jazz legend in Miles Ahead, a film he also directed, previously said the white British star's role as a fictional journalist in the movie helped him secure the funding to ensure the project went ahead.

However, now Don says Ewan's place in the cast is more than a cynical ploy to increase its potential audience as he thinks making the character white rather than black has allowed the film to explore the topic of race more profoundly than would otherwise have been the case.

"I don't know if we had cast Chiwetel Ejiofor in that part that it would have been different, he tells Britain's i newspaper. "From the start, we were going to create that character and I suppose we could have put a black character there – then it would have been five out of six actors being black, rather than four out of six.

"I think the fact that the character is white says more about race relations and black history than if he wasn't."

In his lifetime, Miles often complained that his difficult and rude public image was due to being a black man who refused to be deferential to please white audiences.

Speaking about the musician's reputation as being outspoken in his comments on race, the Ocean's Eleven star says his attitude was more complex than many assume.

"If you know anything about Miles Davis, you would know that his closest musical collaborator was (white Canadian musician) Gil Evans, Miles was about the music," he adds.

"Somebody said to me that he had a problem with white people. Well, he had a problem with white people who had a problem with black people, or those who clubbed him outside his own club."

Miles Ahead has taken nearly a decade to come to fruition, a process which began in 2006 when Miles' nephew, Vince Wilburn suggested Don should play his uncle.

And the filmmaker believes the fact it has taken 25 years after the Kind of Blue composer's death in 1991 to portray his life on screen is down to producers not wanting to take on a project about a black jazz musician.

"People see Miles Davis in a reductive way, playing a type of music that is marginalised," he says. "Something that smells jazz is seen as black and not a safe bet."

Miles Ahead was released nationwide in the U.S. on 1 April (16) and is released in the U.K. on 22 April (16).