Allen is well known for his television work, for which he has won awards in his native Ireland - he has also appeared in ROME for HBO and THE TUDORS for the BBC and Showtime. Recent credits include Mike Leigh's hugely successful ECSTASY at The Hampstead and Duchess Theatres and THE SWEENEY with Ray Winstone, Ben Drew and Hayley Atwell along with ITV's beloved series DOWNTON ABBEY, which won the cast a SAG Award for Outstanding Performance by an Ensemble in a Drama Series for both series 2, 4 and 5. Other credits include the independent feature, GRAND PIANO with Elijah Wood and John Cusack and Big Talk's improvised 3 hander, IN FEAR with Alice Englert and Iain De Caestecker. THE IMITATION GAME in which Allen appeared opposite Benedict Cumberbatch and Keira Knightley won The People's Choice Award at the Toronto Film Festival, opened The London Film Festival was nominated for 5 Golden Globes and 8 Academy Awards. He has most recently been seen playing the lead role in the CBC miniseries, BELLEVUE, opposite Anna Paquin and is currently starring in Nick Payne's multi award winning play CONSTELLATIONS at the Geffen Playhouse in Los Angeles. Allen is currently filming Bryan Singer’s BOHEMIAN RHAPSODY for Fox.