British screenwriter William Nicholson has brushed off Mandela: Long Walk to Freedom’s awards disappointment with a controversial explanation.

Oscar-nominated Nicholson, 66, believes the Nelson Mandela biopic starring Idris Elba was not a huge box office success because 12 Years a Slave “sucked up all the guilt about black people that was available” before his movie was released.

“I think it worked superbly,” he told an audience at the Hay Festival. “I’m incredible proud of this film. Unfortunately it didn’t get the kind of acclaim that I wanted. It didn’t get Oscars.”

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Nicholson, who is believed to have spent 15 years working on the Mandela script, continued: “(America) were so exhausted feeling guilty about slavery that I don’t think there was much left over to be nice about our film. So, our film didn’t do as well as we’d hoped, which was a bit heartbreaking.”

Shape Created with Sketch. Mandela: Long Walk to Freedom Show all 7 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. Mandela: Long Walk to Freedom 1/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela, seen here giving a speech as the leader of the anti-apartheid movement Keith Bernstein 2/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela Keith Bernstein 3/7 Mandela: Long Walk to Freedom Idris Elba and Naomie Harris as Nelson and Winnie Mandela Keith Bernstein 4/7 Mandela: Long Walk to Freedom Naomie Harris stars as Mandela's wife Winnie Keith Bernstein 5/7 Mandela: Long Walk to Freedom Idris Elba stars as Nelson Mandela Keith Bernstein 6/7 Mandela: Long Walk to Freedom Idris Elba and Naomie Harris as Nelson and Winnie Mandela Keith Bernstein 7/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela, seen here in court Keith Bernstein 1/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela, seen here giving a speech as the leader of the anti-apartheid movement Keith Bernstein 2/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela Keith Bernstein 3/7 Mandela: Long Walk to Freedom Idris Elba and Naomie Harris as Nelson and Winnie Mandela Keith Bernstein 4/7 Mandela: Long Walk to Freedom Naomie Harris stars as Mandela's wife Winnie Keith Bernstein 5/7 Mandela: Long Walk to Freedom Idris Elba stars as Nelson Mandela Keith Bernstein 6/7 Mandela: Long Walk to Freedom Idris Elba and Naomie Harris as Nelson and Winnie Mandela Keith Bernstein 7/7 Mandela: Long Walk to Freedom Idris Elba as Nelson Mandela, seen here in court Keith Bernstein

Nicholson then threw modesty to the wind, revealing that Mandela’s failures were “very distressing” after the “really good job” he and director Justin Chadwick had done.

The writer, who worked on 2000’s Gladiator, also blamed Mandela’s death shortly before the film’s release for its lack of success.

“Mandela died as I was in the royal premiere with Will and Kate,” he said. “We were deluged with Mandela stud and after a week we all thought, please take it away, we’ve heard enough about Mandela.”

But Nicholson did not stop there, instead going on to describe the late South African leader’s speeches as “boring” and insisting that most of those used in the film were created by himself.

“I know it sounds outrageous to say a thing like that, but when he came out of prison he made a speech and, God, you fell asleep,” he said.

Steve McQueen's 12 Years a Slave won Best Picture at the 2014 Oscars, while Mandela: Long Walk to Freedom has yet to profit from its $35 million budget.