His first major acting break was the title role in The Adventures of Sir Lancelot on ITV in 1956.
Russell was one of the four original castmembers of Doctor Who in 1963, starring opposite William Hartnell as the Doctor for the first two seasons of the legendary series. Russell continues his involvement with Doctor Who, having lent his voice as a narrator to several of the audio book releases of the 'lost' 1960s episodes. He has also starred in Doctor Who audio dramas and recorded readings of some of the novelisations of Doctor Who episodes. In addition, he has contributed to the Doctor Who DVD range, having participated in several audio commentaries and on-screen interviews since 2002.
He had a small part in an episode of the first series of Blackadder in 1983. On stage, he has acted with the Royal Shakespeare Company, the National Theatre and the Globe Theatre.
From his first marriage to Balbnina Gutierrez, a French actress, he has three children Vanessa, Laetitia and Robert and three grandchildren Elise, Amy and James. Alfred Enoch, his son from his second marriage to Brazilian physician Etheline Margareth Lewis Enoch, plays Dean Thomas in the Harry Potter films.