Idris Elba shared a "surreal" moment with Prince William and his wife Catherine, Duchess Of Cambridge at the screening of his Nelson Mandela biopic when news filtered through that the civil rights icon had died. The Luther actor was joined by the royal couple for the London premiere of Mandela: Long Walk To Freedom in London on 5 December (13), the night the former South African president passed away in Johannesburg. Elba has recalled how he was alerted to the news by the Duchess, who looked visibly shaken several seats away. He tells BBC Radio 2, "Literally halfway through the film Mandela had passed and there was sort of a slight buzz around the auditorium. Interestingly, the Duchess, Kate, sort of turned to me and looked at me as she had her phone and I wondered what was wrong with her because she looked quite emotional, but the film's very emotional. "And my girlfriend looked at me and handed the phone and I looked down and Mandela had passed and it was on a website. It was just the most surreal moment. I looked back at Kate and Prince William and they were just in tears with me. It was just odd. Very odd. "There's a moment in the film and I play older Mandela and he says this one line and it is 'Just open the gate and let me free' - and I kid you not, that that was the one line when we heard the news that was on the screen." Following the screening, the producers of the film decided to break the news to guests. Elba adds, "It only felt appropriate to say what had happened and honestly there was an audible gasp in the auditorium. Some people didn't know, they had their phones off. It was just surreal. "It was very odd, after seeing the credits and I walk on stage. They were giving me a nice round of applause but it was just this moment where I had to say please sit down, and announcing the official speech from President (Jacob) Zuma of South Africa. It was just weird."