British actor Sam Troughton has been forced to sit out the opening night of Sam Mendes' new London production of King Lear after losing his voice mid-sentence while onstage during a preview. The AVP: Alien vs. Predator star, who portrays Edmund in the National Theatre show, struggled to complete his lines on Tuesday night (21Jan14) and director Mendes was forced to step onstage to explain the incident to the audience during the interval. His understudy, Paapa Essiedu, took the actor's place to finish the second half of the play, but leading star Simon Russell Beale, who tackles the title role in the Shakespeare tragedy, admits he had "no idea what was happening" as the drama unfolded before his eyes. Speaking to BBC Radio, he adds, "It must have been terrifying. Apparently his voice just completely gave out." Beale confesses he was panicked as they rushed to rework some aspects of the play, telling Britain's Front Row programme, "There is a bit of you that goes in your head: 'We can't do the second half, we can't throw someone on that's never done this on stage in front of 1,000 people.' But that's not the way we do things and I was really proud of everyone." Essiedu will continue to tackle the role of Edmund for Thursday's (23Jan14) official launch.