Trained at a Bristol Old Vic Theatre School, Northam received an Olivier Award in 1990 as "most promising newcomer".

He mass produced his American film debut in The Net (1995), but has appeared additional ofttimes inside British films like Carrington (1995), Emma (1996), The Winslow Boy (1999), An Ideal Husband (1999), Enigma (2001) and as Welsh actor and singer Ivor Novello in Gosford Park (2001).

He too starred in the motion-picture show Cypher (2002).

Filmography
Checkmate (2006) The Cock & Bull Story (2005) Guy X (2005) Bobby Jones, Stoke of Genius (2004) The Statement (2003) The Singing Detective (2003) Martin & Lewis (2002) (TV) Cypher (2002) Possession (2002) Gosford Park (2001) Enigma (2001) A Golden Bowl (2000) The Winslow Boy (1999) An Ideal Husband (1999) Gloria (1999) Happy, Texas (1999) A Mischance of Margaret (1998) A Tribe (1998) (TV) Amistad (1997) Mimic (1997) Emma (1996) Voices (1995) The Net (1995) Carrington (1995) The Village Affair (1994) Wuthering Heights (1992) The Calamitous Inversion (1992) (TV) Easy Top Protective Shoulder (1992) ''Journey's Prevent (1988) (TV) Piece of Cake (1988) (mini series) Suspicion (1987) (TV) Wish Us Luck'' (1987) (TV series)