A stage-trained British actor who rose to prominence playing incarcerated American Muslim leader Kareem Said on the gritty HBO drama series "Oz" (1997- ). While studying social work, Walker tried out for the Explosive Dance Theatre Company, beginning his career in show business. This led to stage work, including a 1983 turn as a punk in the musical "Labelled With Love", a working class London-set production based on the seminal Squeeze album "East Side Story". TV work followed for the actor, who took a regular role on the BBC sitcom "In Sickness and in Health" from 1985-1987. From 1988-1989, he played PC Malcolm Haines on "The Bill", an ITV police drama.
In 1991, Walker made his feature debut in "Young Soul Rebels", a period piece about London's latter-day soul movement. He was next featured in "Shopping", a 1994 drama chronicling a pair of outlaws (Jude Law and Sadie Frost) who crash stolen cars into shop windows for thrills. Walker returned to series television the following year, playing convict Snoopy Oswald in "The Governor" (1995-96), an ITV prison series produced and directed by Lynda LaPlante and starring Janet McTeer as a female warden. He reteamed with LaPlante in "Supply & Demand" (ITV) in 1997, playing a veteran detective who goes undercover to bust a drug operation.
Work on "Oz" brought Walker to the USA in 1997, and he brought to the role of Said a quiet grace and power, as well as a flawless American accent. Working with producer Tom Fontana, Walker created a fully realized character who showed his human frailties and spiritual sincerity even while engaging in self-righteous grandstanding. Between the third and fourth seasons of "Oz", Walker was featured in "Homicide: The Movie", the 2000 TV-movie reunion of Fontana's acclaimed NBC series. Here he impressed with a pivotal role as a news cameraman who has lost a son to drug abuse and is driven over the edge, shooting a mayoral candidate pushing for drug legalization. Later that year, he was featured in "Once in the Life", a drug-themed drama about two ne'er-do-well brothers, written, produced and directed by as well as starring Laurence Fishburne.