In 1978, Time-Life Television bought the North American rights to a package of Tom Baker Doctor Who episodes, spanning 1974's "Robot" to the recently-aired "Invasion of Time." Unlike the "movie" or "omnibus edits" that were common in the '80s, these shows were broadcast in 30 minute installments, much like the original BBC versions, intended to be shown on weekdays in syndication or PBS.
Figuring that the Doctor's adventures wouldn't be entirely accessible to U.S. and Canadian audiences, and that viewers coming in mid-serial might not be able to pick up the story, Time-Life hired the veteran American character actor Howard Da Silva (best known as Ben Franklin in the movie version of 1776) to record extensive spoken narration that would run at the beginning and end of every episode, explaining who the Doctor was and what he was doing. Da Silva was not associated with science fiction films, nor was he familiar with the show. But since adding the narration resulted in at least two or three minutes getting cut out of every episode's running time, it likely helped some viewers feel less confused. I think they're kind of fun, and add a radio serial cliffhanger quality to the stories; your results may vary.