David Oyelowo became involved with Martin Luther King biopic 'Selma' seven years ago; a project which saw many pitfalls along the way - from financing to director selection - but is now here to tell an extraordinary story of one of the world's biggest heroes.

Oprah Winfrey, David Oyelowo and Ava DuVernay at 'Selma' premiere
David Oyelowo thinks the movie wouldn't have been made without Oprah

It was 2008 when screenwriter Paul Webb first announce the project, which would also bring on board Brad Pitt as a producer, but according to Oyelowo it took seven years in total to complete - a situation that wasn't as much of a drawback as it sounds in hindsight. 'I think it kind of happened at exactly the right time because the preparation for it was layered', he explains. 'There was a physical element to it, emotional, research element interviewing people but then there was a spiritual element to it as well. This man was led by his spiritual conviction and I felt I had to open up to that in order to be able to do it.'

More: Watch the 'Selma' trailer

It took some time for a director to come on board with the project, with Lee Daniels having turned down the job for 'The Butler' and Ava DuVernay eventually signing on in 2013. However, it was the introduction of superstar Oprah Winfrey that Oyelowo believes took 'Selma' to the end. 'I think the film doesn't get made if Oprah didn't come on board', he admits. 'It was a seven year journey for me, the film fell apart several times, and I think [it took] just having a power player like her to come on board and put her weight behind it and be a producer in the real sense not just a vanity producer.'

More: Oprah Winfrey appears at 'Selma' premiere (video)

'Selma' has already been nominated for a total of four Golden Globes, with Oyelowo himself being up for Best Actor. It is set to be released in US movie theaters on January 9th 2015.