Alan "Allen" Leech (born 18 May 1981) is an Irish actor best known for his role as Tom Branson on the historical drama series Downton Abbey. He made his professional acting debut with a small part in a 1998 production of A Streetcar Named Desire, made his first major film appearance as Vincent Cusack in Cowboys & Angels, and earned an Irish Film & Television Awards nomination in 2004 with his performance as Mo Chara in Man About Dog. Leech played Marcus Agrippa on the HBO historical drama series Rome.
Leech was born in Killiney, County Dublin, to David Leech, the CEO of a computer systems company, and Kay Leech, a housewife. He is the third of four children; he has an older brother, Greg, an older sister, Ali, and a younger brother, Simon. He attended St Michael's College. Leech became interested in acting at 11 when he was given the part of the Cowardly Lion in a school production of The Wizard of Oz and found he loved being on stage. He recalled how he immediately decided to become an actor when Peter McDonald told him how acting is a profession on the last night of the production's run.