Diarmaid Murtagh is an Irish actor. He portrayed Leif in the 2013 historical drama television series Vikings, Dimitri in Dracula Untold (2014) and Captain Harpen in The Monuments Men (2014). He first appeared in the 2007 Irish soap opera Ros na Rún. His debut film role was as Captain Harpen in the George Clooney's 2014 war film The Monuments Men. Murtagh played convict Frank Mitchell in the 2019 film The Krays' Mad Axeman.