
Douglas Reith is a British actor and teacher. 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.
Reith was born in Melton, Suffolk. He studied acting at the Webber Douglas Academy of Dramatic Art. 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 an announcer and presenter at BBC Radio 3 for five years before leaving to study Greats at Christ Church, Oxford for four years beginning in 1989. He worked as a teacher, including at Westminster School, before resuming his acting career.
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. He reprised the role in the films Downton Abbey (2019) and Downton Abbey: A New Era (2022). In 2017, Reith was cast in Tim Burton's live-action remake Dumbo (2019). In 2019, he was cast in SAS: Red Notice (2021).

Downton Abbey: The Grand Finale
Richard Grey
2025

Downton Abbey: A New Era
Lord Merton
2022

The War Below
Field Marshal Haig
2021

SAS: Red Notice
Sir Charles Whiteside
2021

Professor T
Dean · (18 episodes)
2021

Downton Abbey
Lord Merton
2019

Pandora
Prescott Fleming · (1 episode)
2019

Dumbo
Sotheby
2019

Fearless
Justice Angus Hill · (6 episodes)
2017

The Crown
Admiral Leach · (1 episode)
2016

Agatha Raisin
Lord Pendlebury · (1 episode)
2016

Serial Teachers 2
Le chef de la sécurité
2015

Outlander
Professor Brown · (1 episode)
2014

Rush
Awards Presenter
2013

W.E.
Lord Brownlow
2011

Downton Abbey
Lord Merton · (8 episodes)
2010

Enid
BBC Interviewer
2009

Ancient Rome: The Rise and Fall of an Empire
Metellus · (1 episode)
2006

The Queen
Lord Airlie
2006

The Queen's Sister
Horace Featherstonehaugh
2005

Elizabeth I
Jude · (2 episodes)
2005

Elizabeth I
Judge · (2 episodes)
2005

Rose and Maloney
(1 episode)
2002

Bloodlines: Legacy of a Lord
1998

The Prince and the Pauper
Chamberlain · (6 episodes)
1996

An Englishman Abroad
Toby
1983

The Happy Autumn Fields
Fitzgeorge
1980

Minder
Bellars · (1 episode)
1979

International Velvet
Howard
1978