He was known for his portrayals of Vernon Dursley in the Harry Potter films (2001–2010), Uncle Monty in Withnail and I (1987), and Henry Crabbe in Pie in the Sky (1994–1997).
Griffiths had supporting roles in such critically acclaimed films as Chariots of Fire (1981), The French Lieutenant's Woman (1981), Gandhi (1982), A Private Function (1984), Venus (2006), Ballet Shoes (2007), and Hugo (2011).
He also acted in The Naked Gun 2½: The Smell of Fear (1991), Sleepy Hollow (1999), The Hitchhiker's Guide to the Galaxy (2005), and Pirates of the Caribbean: On Stranger Tides (2011).
[11] In 1981, he also gave a memorable performance as Chilean secret police victim William Beausire in an edition of the BBC Prisoners of Conscience series.
[12] Griffiths went on to supporting roles in a number of major films, including The French Lieutenant's Woman, Chariots of Fire and Gandhi.
[13] On stage, in 1985–1986, he performed the role of Verdi in Julian Mitchell's After Aida, in Wales and at the Old Vic Theatre in London.
Some of his most memorable roles included supporting parts in films as Gorky Park (1983), Withnail and I (1987), King Ralph (1991), The Naked Gun 2+1⁄2: The Smell of Fear (1991), Blame It on the Bellboy (1992), Guarding Tess (1994) and Sleepy Hollow (1999).
[14] Later, he was seen as the short-tempered Vernon Dursley in the Harry Potter series, appearing in five of the eight films: Philosopher's Stone, Chamber of Secrets, Prisoner of Azkaban, Order of the Phoenix and Deathly Hallows – Part 1.
[16] In 2004, he originated the role of Hector (the teacher) in Alan Bennett's play The History Boys, directed by Nicholas Hytner, winning the 2005 Laurence Olivier Award for Best Actor.
[19][20] Later in 2009, he replaced Michael Gambon as W. H. Auden prior to the premiere of The Habit of Art at the National Theatre, once again directed by Hytner.
Griffiths was awarded an honorary degree from Teesside University in 2006 and was appointed an Officer of the Order of the British Empire (OBE) in the 2008 New Year Honours.