Movies:
* The Secret Garden (1993): As Dickon
* The Borrowers (1997): As Spiller
* The Borrowers (2011): As Spiller (voice)
* The Golden Compass (2007): As The Master
* Alice in Wonderland (2010): As The Mad Hatter (voice)
* The King's Speech (2010): As The King's Doctor
* Cloud Atlas (2012): As The Doctor (Korean Version)
* The Imitation Game (2014): As The British Military Chief
* Darkest Hour (2017): As Sir Robert Vansittart
* The Favourite (2018): As Lord Godolphin
* The Personal History of David Copperfield (2019): As Mr. Wickfield
* The Electrical Life of Louis Wain (2021): As Dr. Ross
Television:
* Casualty (1986-present): As various characters (multiple episodes)
* Inspector Morse (1987-1993): As Various Characters (multiple episodes)
* The Bill (1984-2010): As Various Characters (multiple episodes)
* Jonathan Creek (1997-2016): As Various Characters (multiple episodes)
* Midsomer Murders (1997-present): As Various Characters (multiple episodes)
* Spooks (2002-2011): As Various Characters (multiple episodes)
* Doctors (2000-present): As Various Characters (multiple episodes)
* EastEnders (1985-present): As Various Characters (multiple episodes)
* Holby City (1999-present): As Various Characters (multiple episodes)
* Merlin (2008-2012): As Lord Athelstan
* Call the Midwife (2012-present): As Dr. Turner (recurring role)
* The Crown (2016-present): As Lord Mountbatten (recurring role)
* The English Game (2020): As The Rev. A.C. Selous
* The Tourist (2021-2022): As Lachlan
* The Essex Serpent (2022): As Dr. Thomas Cope
This list is not exhaustive but includes some of his most notable works. He's known for his versatility and for frequently portraying authority figures, doctors, and historical figures.