Before being selected to replace Peter Davison as the Doctor, Baker was an established television actor, his most notable role having been that of Paul Merroney in The Brothers.
Before taking over as the Doctor, he had played another character in the series (in the episode "Arc of Infinity"), being the only Doctor to have done so. He also appeared in Blake's 7. He is largely thought of as the least successful Doctor, though he suffered from inconsistent writing and a long hiatus as the show was moved back from the spring to the autumn schedules, and was sacked from the role at the insistence of BBC management wanting to refresh the show.
Since leaving Doctor Who he has continued to act, mainly on the stage.
Since the death of his son in 1983 he has been active in raising the profile of Sudden Infant Death Syndrome research, and is the current chairman of the Foundation for the Study of Infant Deaths.