"In a 2013 production of Harold Pinter's "The Dumb Waiter" at The Print Room, Armstrong played Gus alongside Clive Wood as Ben.Matt Trueman of "The Telegraph" called Wood and Armstrong "two perfect Pinterians," and Fiona Mountford of "The Evening Standard" wrote, "Armstrong, always an actor of easy geniality, flourishes in particular with this short, sharp, light-footed humour."