Image caption The film is based on Mandela's autobiography

A new screen biopic of Nelson Mandela does not shy away from the less flattering aspects of his character, according to its British star.

"It was important we had both sides, the good and the bad," said Idris Elba.

Early scenes in Justin Chadwick's film show Mandela as a womaniser who was violent to his first wife Evelyn.

"I didn't want to deface Mr Mandela in any way," the Luther actor continued. "But I didn't want to portray him in a way that wasn't honest."

Elba was speaking at the Toronto Film Festival, where Mandela: Long Walk to Freedom had its world premiere this weekend.

Based on the former South African president's autobiography, the film charts his early life as a lawyer, his political activism and the 27 years of imprisonment that preceded his democratic election in 1994.

Naomie Harris, also British, plays Mandela's second wife Winnie in Justin Chadwick's two-and-a-half hour drama.

'Brave choice'

Image caption [L-R] Terry Pheto, Naomie Harris, Idris Elba, Lindiwe Matshikiza star in director Justin Chadwick's film

The film has had a mixed reception from critics, with one calling it "more dutifully reverential than revelatory or exciting".

"We've seen the saintly Mandela we all know and love," continued Elba, who did not meet "Madiba" before embarking on the project.

"It was important for us to take the audience on a journey prior to that and understand who he was."

The internationally revered anti-apartheid campaigner, now 95, was released from hospital last week after three months of treatment for a recurring lung infection.

"Like everybody I've been very concerned for his health but I've been keeping optimistic," Elba told reporters on Sunday.

According to Chadwick, the Hackney-born actor was the right person for the biopic despite being from England and bearing little physical resemblance to its subject.

"There were other obvious choices, but Idris was the brave choice," said the director, whose other credits include the BBC's 2005 dramatisation of Dickens' Bleak House.

"He doesn't look like Madiba, but we weren't going for a lookalike, soundalike version."

"Idris managed to capture the Mandela magic," agreed Terry Pheto, the South African actress who plays Evelyn in the film.

Industry reviews

Morgan Freeman, Danny Glover, David Harewood and Sidney Poitier are among the others to have portrayed the beloved statesman on film and television.

Image caption Elba has found success as a rule-breaking detective in BBC One's Luther

Elba, whose other films include summer blockbusters Thor and Pacific Rim, has been singled out for praise by critics who have seen the film in Toronto.

"It takes a commanding actor to fill the shoes of the man most instrumental in ending institutionalised oppression in South Africa," wrote David Rooney in the Hollywood Reporter.

"The charismatic Idris Elba proves equal to the task."

According to Screen International, though, the film is "too tasteful and conventional to offer much insight into the remarkable man it wishes to celebrate".

"It doesn't have much of a point of view about its narrative, serving more as a rote recitation of memorable moments."

Mandela: Long Walk to Freedom is one of several Toronto titles this year to draw their inspiration from real-life figures.

Julian Assange, Jimi Hendrix and Britain's Got Talent winner Paul Potts also feature in films in this year's line-up.

The launch of Chadwick's film coincides with the UK release of Diana, a biographical drama about Diana, Princess of Wales that drew a withering response from the British media.

The Toronto International Film Festival continues until 15 September.