LOS ANGELES – British actor Idris Elba is having what he describes as a “beautiful moment” in his career. His off-screen life, though, is another story.

This summer, Elba starred in Guillermo del Toro’s special-effects action thriller “Pacific Rim,” in which he transformed the rather moldy line, “We are canceling the apocalypse,” into something akin to Shakespeare.

The third season of his acclaimed British detective series, “Luther,” for which he won a Golden Globe in 2012, recently aired on BBC America, and he’s reprising his role of Heimdall, the buff, Asgardian warrior-god gatekeeper, in “Thor: The Dark World.”

And he’s garnering rave reviews – not to mention awards buzz – for his complex performance as the late Nelson Mandela, the legendary South African leader who helped end apartheid, in the new biographical drama “Mandela: Long Walk to Freedom.” But during a recent interview, the 41-year-old Elba admitted he’s “numb” to the attention and praise.

“It’s weird at the moment,” the strikingly handsome actor said recently over lunch at the Mondrian hotel on Sunset Boulevard.

“My dad died eight, nine weeks ago,” he said, quietly. “He was 76. He died of lung cancer. I am having to deal with grief and it has taken a profound effect on me.”

Elba doesn’t want to sound ungrateful for his professional good fortune. “I put on a smile, put on the suits and I go on the red carpet. I do the work, and I’m doing it because that is what my old man would want me to do. He was very proud of me.”

The actor, who is an only child, used his father, Winston, as the basis for his performance. His father immigrated to London from Sierra Leone; his mother, Eva, is from Ghana.

Though from different African countries, Elba said, his father and Mandela had the same cadence in their speech. There were other similarities in their behaviors, from the way they crossed their legs to holding their fingers while talking, which helped him immeasurably in bringing Mandela to life. “My dad had a big silver ball of hair and Mandela has that, so that was my framework,” he said.

Elba, who exudes as much charisma in person as he does on screen, made his first impression on American audiences in 2002 with his explosive performance as Stringer Bell, the aspirational second-in-command to a Baltimore drug kingpin in HBO’s award-winning series “The Wire.”

Over the last decade, the actor has appeared in numerous films and TV series including NBC’s “The Office” (he played a rival to Steve Carell’s regional manager), the 2007 Tyler Perry melodrama “Daddy’s Little Girls,” as well as Ridley Scott’s 2007 “American Gangster” and 2012’s “Prometheus.”

He’s also moonlights as a DJ. “I am hired specifically for my hard, progressive house music,” said Elba. “It’s so different from this world. Nobody cares about who I am when I am out playing the music. It really grounds me. It’s a side of my creativity I can’t let go of.”

A singer and songwriter, Elba just recorded an album in South Africa inspired by his experience making the movie in the country. “I call it character music,” Elba said. “It’s the first time of really marrying what I do in the film with the music.”

At first, Idris, who plays Mandela from his 20s through his late 70s, was reluctant to take on the role of the lawyer and anti-apartheid activist, who spent 27 years in prison before becoming the country’s first democratically elected president.

Not only did he feel he was too young to play the role, “I am actually four shades too dark,” said Elba.

But director Justin Chadwick had an instinct about Elba.

“He’s a subtle actor that totally inhabits a role,” said Chadwick in an email. “The producers had imagined I’d cast a Hollywood star, but I loved that Idris carried no baggage into whatever role he plays. We weren’t going for a look-alike version, but wanted to catch the spirit of the man.”

Elba, Chadwick added, “is a true gentle man, very warm and generous. He is also fearless. And that’s how people described Mandela the young man to me.”

The actor recalls talking to Chadwick about the role while he was filming “Pacific Rim” in Toronto.

“He sat with me, watched me work and we talked and talked,” said Elba in his strong British working-class accent. “I started to warm up to the idea. But I was really scared. I thought, ‘Oh, my God, if I mess this up, what the hell? I’ll never work again.’”

A lot of his fears were laid to rest when he met Naomie Harris, who plays Mandela’s second wife, Winnie, the naïve young social worker who transforms into a defiant militant.

“The on-screen chemistry was amazing,” said Elba. “I am looking at Winnie and Nelson, I am not looking at Naomie and I. The love feels so real.”

Though he never got to meet the 95-year-old Mandela, who died this month, Elba has become close to his family. At the premiere in November in South Africa, Mandela’s daughter Zinzdi even said to him, “Come here, Dad,” so they could pose together for photos.

Elba insisted that he spend a night in one of the dehumanizing small cells on Robben Island, where Mandela spent 18 years in prison. It is now a museum.

The officials turned him down several times. Frustrated, Elba even contemplated getting into a brawl in a bar so he could spend the night in jail. But finally, the Robben Island officials allowed him to stay in a “punishment” cell.

“When you are locked in the room you are powerless,” said Elba. “I was lucky I only had 24 hours. But it just put it into context and what his frame of mind was to have endured for that long of time.”

Chadwick said he always knew that Elba would be “brilliant” as the young Mandela. “It was the older, more recognizable Mandela that was the challenge that we had to catch.”

Because the indie film didn’t have deep financial pockets, “we had to be canny with our resources … we had to shoot totally out of sequence,” said Chadwick.

In fact, in one day Elba had to do a quick transformation from a 40-year-old Mandela to the elderly man in his 70s.

“His walk and his body language was breathtaking,” said Chadwick. “He became Mandela.”

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