 In 2017 Armstrong appeared in Joe Wright's war drama "Darkest Hour", his major studio debut.Armstrong performed in the BBC radio plays "Girl from Mars" in 2008 and "Hitched" in 2010, and he read the story "Gifts" by Garry Kilworth as part of a Christmas radio programme.In 2011, he co-starred with Richard Briers and Edna Doré in the Radio 4 drama "A Shoebox of Snow".