Frederic Wilhelm C.J. Sjöström (born 8 January 1987) is an English actor and model, best known for playing Cormac McLaggen in the Harry Potter film series and Luke in the 2012 musical comedy film Pitch Perfect. He starred as Adam Cromwell on the dramedy series UnREAL, which premiered on Lifetime in June 2015. He starred as Brit Vayner in the 2016 Michael Bay war film, 13 Hours: The Secret Soldiers of Benghazi. And in April 2016, he will play Dickon Tarly during the sixth season of the HBO fantasy drama series Game of Thrones.