Began his career in advertising as an assistant producer and turned to amateur filmmaking in the late 1950s. In the mid-1960s Watkins was commissioned by BBC-TV to make two feature-length "docudramas" incorporating a quasi-newsreel style and nonprofessional actors. The second of these, "The War Game" (1966), graphically portrayed the nightmare of nuclear war and was banned from broadcast. It was subsequently released in theaters and earned a Best Documentary Oscar in 1966.

Watkins enjoyed a modest reception with the uneven but striking commercial feature film, "Privilege" (1967), but has subsequently worked primarily in the documentary genre, based in various Scandinavian countries. His most recent film, "The Journey" (1986), is a 14-1/2-hour epic address such issues as the arms race and global hunger.