Other notable film and television roles include John Hanning Speke in Mountains of the Moon (1990), Larry Winters in Silent Scream (1990) for which he won the Silver Bear for Best Actor at the Berlin International Film Festival, Manfred Powell in Lara Croft: Tomb Raider (2001), Brother John in Song for a Raggy Boy (2003), the title role in Jack Taylor (2010–2016), Sir Richard Carlisle in Downton Abbey (2011), James Willett in Eye in the Sky (2015), Bruce Wayne in Titans (2019–2021), Magnus MacMillan in The Rig (2023–present), and Dr. Pete Nichols in Silo (2023–present).

Ian McDiarmid plays Henry Fielding (author of the novel Tom Jones) who along with his brother, John, started London's first professional police force.

[14] From 2010 to 2016, Glen played the title character in the Irish TV crime series Jack Taylor, adapted from the novels by Ken Bruen, and set in Galway, Ireland.

[17] The same year, he starred in a new four-part BBC Radio 4 adaptation of The Count of Monte Cristo, written by Sebastian Baczkiewicz, and directed by Jeremy Mortimer and Sasha Yevtushenko.

[19] He had been due to appear in the full run until late February 2014,[20] but was forced to withdraw early to recover from illness, with his role taken by his understudy Patrick Cremin and then by William Houston, who joined the cast at around the same time as Glen's departure.

[23] The same year, he starred as William Carr in Operation Napoleon, a thriller directed by Óskar Þór Axelsson and based on Arnaldur Indriðason's best selling book of the same name.