Steven Knight Creator, Producer Anthony Boyle Arthur Guinness Actor Louis Partridge Edward Guinness Actor Emily Fairn Anne Plunket Actor Fionn O'Shea Benjamin Guinness Actor James Norton Sean Rafferty Actor Niamh McCormack Ellen Cochrane Actor Seamus O'Hara Patrick Cochrane Actor Jack Gleeson Byron Hedges Actor Dervla Kirwan Aunt Agnes Guinness Actor Danielle Galligan Lady Olivia Hedges Actor David Wilmot Bonnie Champion Actor Cahal Bannon Producer Howard Burch Producer Elinor Day Executive Producer Martin Haines Executive Producer Karen Wilson Executive Producer Mounia Akl Director