He is best known for his role as Lord Merton in the television series Downton Abbey (2010–2015), as well as its two follow-up films.
[1] He began acting in the late 1970s, beginning with an appearance in International Velvet (1978) alongside Tatum O'Neal and Christopher Plummer.
He worked as a teacher, including at Westminster School, before resuming his acting career.
[3] Reith joined the cast of Downton Abbey as Lord Merton in 2012, and alongside the cast was nominated for the Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Drama Series at the 23rd Screen Actors Guild Awards.
[5][6] In 2017, Reith was cast in Tim Burton's live-action remake Dumbo (2019).